It's not the software. The software tries to load the account screen and even shows the AT&T logo. It's communicating with the same server that AT&T's website communicates with and submits the IMEI number but returns the same error message rather than showing the plans. It's the same error message that you get on an AT&T iPad if you try to purchase service using a SIM card that was previously used on a different iPad, which is also related to a bad IMEI number.
This does not correlate with my experience.
I purchased the cheapest monthly AT&T iPad service (no auto-renewal) on my original iPad, then acquired an iPad 2 in the same month. I put the active iPad SIM in the newer device and it had no problem continuing service. At the end of the month, the service terminated correctly. A few months later, I bought another month's worth of 3G service without any problem.
More recently, I tried an AT&T GoPhone SIM (which had an active data package) in my iPad 2. It could not connect to AT&T's cellular 3G data network until I installed a custom APN (from
http://www.unlockit.co.nz) for AT&T's GoPhone network. Then it worked fine. When I went through the iPad's interface to view the cellular account, it did not connect to the AT&T website.
There is something in the iPad's software that identifies the regular AT&T iPad cellular data SIM with the website for purchasing data plans.
Using the GoPhone SIM in an iPad is an option
for those who have very minimal cellular data requirements (rare instances when you don't have WiFi and need access to e-mail, maybe the web, etc.).
One difference with the GoPhone SIM is that unused cellular data will rollover to the next month provided you purchase a new data package before the end of the month (yes, there are auto-renewing data packages).
The GoPhone data packages are:
500MB for $25
100MB for $10
5MB for $5
You can add $100 of GoPhone credit (talk time) which won't expire for a year even though the data packages expire after a month. You can purchase one 500MB data package for $25, followed by four months of 5MB data packages at $5 apiece. That works out to 104MB for $9 per month.
This is definitely pricier per megabyte than the regular low end AT&T iPad monthly service (250MB for $15), but if you're not using 250MB, you're throwing some money away since the regular iPad data service doesn't have rollover data.
If you are consistently using an average of less than 200MB per month in cellular data on an iPad, the GoPhone solution should be investigated as a reasonable alternative. If you are using less than 120MB of cellular data, this is a really good solution (which is why I'm currently keeping a GoPhone SIM alive for my iPad).
If you think you're going to have a month with massive iPad cellular data (e.g., a vacation), you can put the original iPad SIM back in and buy one of the bigger plans. (You would have to delete the GoPhone-specific APN configuration file.)
Note that I have swapped GoPhone SIMs between my iPhone 4S and my iPad 2 without any issue whatsoever. There is nothing with the GoPhone service that prevents the regular ad hoc tethering hacks. I have the Handy Light app and I am perfectly able to tether (damn, it is expensive per megabyte).
Here in California, there are no additional surcharges to GoPhone service: no taxes, fees, etc.
Moreover, I have quoted "full retail" pricing for GoPhone services. It's pretty easy to find discount GoPhone refill cards. CallingMart.com typically has monthly deals where a $100 GoPhone refill card can be purchased at $90 (I find the discount codes on their Twitter feed). Buy the GoPhone refill card and get the e-mail with the activation code in minutes. This like buying iTunes Gift Cards at some online retailers at a discount.
Please remember that my comments are highly specific to people who have
minimal cellular data requirements. I use my iPhone and iPad the way I would normally use them (95% of the time on WiFi). Combined, I am spending maybe $20 per month in cellular service with all discounts included.
The biggest takeaway is that if you're using a GoPhone SIM, you can get what you pay for, but if you're not getting much, you can pay considerably less.
