How much do you pay for unlimited 4G at T-mobil? Same as you paid before you switched?
I didn't get data service when I had AT&T. I was paying $70 just for unlimited text and talk, no data. When I switched over, I got unlimited text and talk for $50 with a 500MB data plan at 4G and then it drops down to what I believe would be like dial up speed. But I don't use much data since I use the phones built in wifi for internet when it is available. I don't send out picture messages very often, nor do I receive many of them either.
I upgraded my 3G to 5G about 5 months ago.
As of then they do grandfather and I am still on the unlimited data plan.
They haven't always grandfathered and I almost switched carriers because about a year ago I asked about staying on unlimited data with AT&T and they said tough-luck, so I had to stay with my 3G longer than I normally would have.
Apparently there was a wave of people switching from AT&T because people had to upgrade their 3G phones - so AT&T relented and now offer grandfathering if you stay on the same plan. But be careful, although you can still upgrade parts of your plan (non-data parts) and still be grandfathered for data, AT&T customer service will try periodically to sell you a plan that will end your grandfathering. So be careful and ask.
Yes. You move to a 5s on ATT and keep your unlimited data plan. Apple offers this option ny default if you upgrade using the Apple App. Upgrading through the ATT site will drop your unlimited plan by default, but people say you can add it back if you pay attention during your purchase.