My old phone (HTC Inspire), was stolen, and I wasn't yet eligible for an upgrade, however, my dad was. I ordered a new phone (Samsung Galaxy S2 Skyrocket) with his upgrade. I got a replacement SIM card from ATT, and put it in the phone. The problem is that now my data plan is for non-LTE smartphones, and won't let me use mobile data on my new phone. Also, my dad is being forced into an LTE plan with his Iphone 4. I tried to change the data plan online, but when I selected the LTE plan, it told me it conflicted with my older data plan, which is supposedly unchangable. How do I fix this problem?