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You can do it like this:

1. Take new phone out of the box and do NOT turn it on.
2. Remove the new sim and set it aside.
3. Take the sim from your 5s and put it in the new iPhone.
4. Turn it on and set it up however you like.
5. Erase your 5s and send it to your son.
6. He inserts his 5 sim into his "new" 5s and he sets up it up.

At no point do you have to call AT&T. What do you do with the sim that was originally inside the 6? Nothing!

Yes that sim is tied to his number but it's never going to be activated so his current sim will stay working. Since att/apple is mailing you a phone, the sim inside has to stay inactive so you can continue to use your current phone. It would have to stay inactive indefinitely because how they don't know how long it takes to get your phone. What if you are on vacation, what if it gets lost in the mail, etc?

I used this exact procedure going from a 5 to 5s and will do it again today with my 6. The upgrade I stole that time from our large corp account still has his/her phone working after a year and the original sim from the 5s is still sitting in a drawer somewhere. So at the end of today, the sim in my 6 will have gone from 5 to 5s to 6 without ever calling AT&T.

Bam!
thank you. Exactly what I am going to do!

Appreciate the detail in your response, seems to be a ton of confusion. Even on ATT.net they say you have to go into the store or call, why I have no clue.
 
Yeah...that is why I am just going to ATT instead of Apple to buy the phone this morning. Never again will I give my upgrade to someone else - putting me in this position. Two years from now I can just preorder or go to Apple and avoid all this hassle.
 
Bam!
thank you. Exactly what I am going to do!

Appreciate the detail in your response, seems to be a ton of confusion. Even on ATT.net they say you have to go into the store or call, why I have no clue.

So has anyone tried this yet today? ATT reps keep saying that the "sim technology is different" and that just putting my ip5 sim in my ip6 won't work. I'd rather just do that, lessen the chance of someone on ATT's end messing up and deactivating my mom's phone (I used her line for the upgrade). Since I'm in DC and she's in Pittsburgh, I can't help her much beyond telling her that if her phone "breaks", to go the ATT store.
 
So has anyone tried this yet today? ATT reps keep saying that the "sim technology is different" and that just putting my ip5 sim in my ip6 won't work. I'd rather just do that, lessen the chance of someone on ATT's end messing up and deactivating my mom's phone (I used her line for the upgrade). Since I'm in DC and she's in Pittsburgh, I can't help her much beyond telling her that if her phone "breaks", to go the ATT store.

Well I sure HOPE it will work! I'll know for sure a few mins after Fedex arrives this today. I live in walking distance of a mall with an Apple store. After dropping off the kid at school, I went over to get Starbucks and just gawk at the massive line. It's insane and so glad I don't have to deal with that.
 
Take a look at ATT site it says;

Choose your activation method based on whether you want to:
Activate your device on the upgrade-eligible line.
Activate your device on a different line than the upgrade-eligible line, also known as a cross upgrade. This occurs when you want to use the upgrade eligibility of one line to upgrade the device on another line.

Activate your device on the upgrade-eligible line
Select the method that best meets your needs to activate your device on the upgrade-eligible line:
Activate online by visiting att.com/activations and completing the online form.
Activate over the phone by calling 866.895.1099 and accepting the Terms & Conditions.

Activate your device on a different line than the upgrade-eligible line
To activate your device on a different line than the upgrade-eligible line:
From a different phone than the line that you used for your upgrade, call 800.331.0500.

When prompted, enter the wireless number for the upgrade-eligible line.
At the next prompt, press 2 to activate a different wireless number on your device.

Stay on the line and an AT&T Customer Service representative will help you complete the activation.
 
Take a look at ATT site it says;

Choose your activation method based on whether you want to:
Activate your device on the upgrade-eligible line.
Activate your device on a different line than the upgrade-eligible line, also known as a cross upgrade. This occurs when you want to use the upgrade eligibility of one line to upgrade the device on another line.

Activate your device on the upgrade-eligible line
Select the method that best meets your needs to activate your device on the upgrade-eligible line:
Activate online by visiting att.com/activations and completing the online form.
Activate over the phone by calling 866.895.1099 and accepting the Terms & Conditions.

Activate your device on a different line than the upgrade-eligible line
To activate your device on a different line than the upgrade-eligible line:
From a different phone than the line that you used for your upgrade, call 800.331.0500.

When prompted, enter the wireless number for the upgrade-eligible line.
At the next prompt, press 2 to activate a different wireless number on your device.

Stay on the line and an AT&T Customer Service representative will help you complete the activation.

Yep, saw that.
But others claim this is not necessary, and runs the risk of human error disconnecting the other line/sim in the process.

If that happens, my son's line would go dead.
 
Has anyone tried activating their iPhone cross upgrade/upgrade swap yet by calling the 800-331-0500 att number?

Did it work without hassle and without deactivating the line that the upgrade was purchased on? And without the need to go get new sim cards?

Any info would help. I'm not sure whether to just try swapping sims or to call the att number to activate.
 
I am also eagerly awaiting a report on someone else's experience. I, too, would like to avoid disrupting service on the SIM currently associated with the line used to upgrade.

I ordered my iPhone 6 via upgrade to my father-in-law's line on a family plan I maintain, but based on the guide mention above intend to activate while my nano-SIM associated with my work number is installed. I don't want to disrupt my father-in-law's use of his iPhone 4, and him getting a replacement micro-SIM, activating, and installing it over the weekend is not an option in his location.
 
Yep, saw that.
But others claim this is not necessary, and runs the risk of human error disconnecting the other line/sim in the process.

If that happens, my son's line would go dead.

Just so you know, I swapped sims and all is well. There has been some rumor about needing special sims for the NFC to work. That appears to be incorrect information based on some older NFC/SIM tech for phones that didn't have built in NFC chips like the 6 does.

Should it turn out that we actually do need new sims, it's not a big deal we can hit up an AT&T store a few weeks from now when things settle down.

But to be clear, I swapped sims, tested 4G, LTE, inbound, outbound and visual voicemail and everything works 100%.

Swap your sims and send your 5S to your son. My son wants my 5S but he's just in kindergarten so i'm going to say no for now!
 
I ended up calling ATT. He fixed the line swap in their system and put the new phone under my number.

No sense in guessing. He did advise swapping sims would work for about 24 hours. No idea why but he claimed it would inactivate if I had not called in

Take this for what it's worth. He did seem knowledgeable.
 
For anyone interested, I activated the new iPhone 6 with my company SIM card installed and that process deactivated my father-in-law's old SIM card. Not what I was hoping for based on the advice of an earlier poster. This will have to be resolved on Monday with a new micro-SIM.
 
My wife's iPhone on my account is eligible for a full subsidized upgrade. I want to purchase the iPhone 5S and transfer the upgrade since my iPhone 5 is not eligible.

From what I understand, I need to purchase the iPhone 5S using my wife's number and then call AT&T to transfer the upgrade to my number.

Has anyone actually done this? This will be the first time for me and I want to make sure I do it correctly. What is the correct process so I don't screw this up.

Thanks.

I have done this twice. Did it again last night. I called AT&T CS and gave them the IMEI number and CCID number from the back of the box. They deactivated my iPhone 5S and when I plugged the iPhone 6+ into iTunes, it activated it on my current phone line. It kept showng me my daughter's phone number on the 2nd or 3rd screen (she didn't want a new phone) so I was afraid I'd be deactivating her phone, but it went great!
 
I have done this twice. Did it again last night. I called AT&T CS and gave them the IMEI number and CCID number from the back of the box. They deactivated my iPhone 5S and when I plugged the iPhone 6+ into iTunes, it activated it on my current phone line. It kept showng me my daughter's phone number on the 2nd or 3rd screen (she didn't want a new phone) so I was afraid I'd be deactivating her phone, but it went great!

This sounds like the best option. So for no moment was your daughter's SIM/service disrupted by the whole process?

Getting a 6 with my mother's upgrade, and giving her my 5.

Also, do you think they can do this in-store at AT&T instead of calling CS?
 
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