So, I have my family's 4 phones on 10GB mobile share. They are all BYOD - no contracts, none on NEXT. Total of $160/mo not including taxes. Now, say I want the new iPhone 6, 16GB on only one of the lines. According to ATT, the NEXT18 plan will be 24 payments of $27.09, but the line will be credited $25 per month. Here are my questions: Does my bill then increase by only $2.09 per month? If I don't trade it in at 18 months, do I lose the $25 credit? If so, when - at 18 months or at 24 months when the payments are done? Or is the $25 credit permanent while in the NEXT program?