Last year I bought a 6plus and used it for few weeks. I got the T-mobile version from Apple online store, And I put my ATT sim in it. Everything works fine except the mobile hotspot. Everytime I tried to turn it on, it pops up a notification that told me to call att support #. As I said I only used it for few weeks last year, Is this a common problem for Tmobile version that with a att sim in it? Or this year should I get T-mobile version from apple online store or ATT version from ATT website?