Why isn't my phone allowing me to use my data plan?

[iMore Question]

4g internet

I have an unlocked IPhone 6 from T-Mobile. I live overseas and only need a U.S. number for about 45 days a year. I returned to cal on holiday and re activated my AT&T number. I can make calls bit it's not allowing me to use my data plan. AT&T says it's the phone any ideas???

 

[Tartarus]

Re: 4g internet

Did you try to disable and enable Celullar Data on your device yet?