Just for the record, I have had iPhones on ATT with no data plan for a couple of years. I already had the numbers, just bought the phones used. In each case ATT told me I had to have a data plan and I told them my contract was years out and I did not need a data plan. It worked. This was for two lines on a family plan & a third line did have a data plan.

Those plans still had data available so I would pay if any data was used. I kept data turned off on the phones so they only did data on wifi. This also disabled MMS texting and texts to multiple numbers.

I tried the TMO $30 prepaid plan but it doesn't work in China. In the end I got a RAZR Maxx & two years to life on Verizon.