How can I check if my phone is unlocked?

If you didn't get a message that your SIM isn't supported and you seem to have an AT&T signal and carrier information listed then it seems like it's unlocked.

 

T-Mobile iPhone 7 have the intel modem. They don't have cdma radios. So no Sprint or Verizon usage.

 

If it works with T-Mobile, and is unlocked, it will more than likely work with T-Mobile AND AT&T.
But, like others have said, Verizon and Sprint are CDMA carriers...

 

Sounds like it's unlocked.
What model iPhone?

 

That could potentially be because your phone might not support CDMA. What iPhone are we talking about exactly?

 

So you are saying a T-Mobile SIM works and an AT&T SIM works, but a Sprint SIM gives a not supported error?

 

Sprint has over 14 different SKUs for SIM cards. A SIM card for a Sprint iPhone 5 will not work in a 5c or above. A Sprint Android SIM will not work in an iPhone and vice versa.

When it comes to Sprint you have to have the right SIM card for the device. AND you have to give Sprint the IMEI of the device so it works with that SIM. Sprint is not like the other carriers where you can just swap SIMs if you feel like it.

Assuming your device has CDMA capability and can use at least one of Sprint's bands (as has already been mentioned).

 

Realistically if you restore in iTunes that should give a message that your device is unlocked if it's actually unlocked (at least it used to).

 

So it's not unlocked.
It sounds like it's locked to T-Mobile.

 

Agreed. If the phone were unlocked, an unactivated AT&T SIM would show "No Service." If the phone is locked to T-Mobile, it would say "SIM Not Supported."

 

I wonder why 40 days? So do you intend just to wait it out?

 

What?
Activation lock is just the icloud device Apple ID lock and has nothing to do with carrier unlock or using other sims.
And then they told you its unlocked but they'll unlock it after 40 days?
I dont get it...

 

This makes sense. The phone is locked, but T-Mobile will unlock it for the OP. This just have a 40 day 'requirement'.

Unlock eligibility for monthly phones, tablets, and mobile Internet devices

• The device must have been active on the T-Mobile network for at least 40 days on the requesting line.

 

Doesn't seem right. It's unlocked, but still tied to T-Mobile for the next 40 days? What happens then? If it's unlocked, then it's unlocked.

 

The OP said that when he put in At&t sim it said unsupported. So it's probably locked. Either he misunderstood the T-mobile rep, or the rep misspoke. Sounds like T-Mobile will unlock after 40 days.

 

So it's not unlocked and they will unlock it after the 40 days are up.

 

Interesting. Thanks for sharing this. So, the 40 days is just policy then, with no other significance.