Why am I charged a month in advance, for a simple change in my data plan -- from 10gb to 20gb? On my last bill, I was refunded $80 for the 10gb plan, and charged $140 for my new 20gb plan. That I understand. But why am I charged another $140 for an advanced payment on that 20gb plan? (In the end, I'm being asked to pay $200 for last month, even though the 20gb plan is only $140.) I'm not a new customer -- been one for 20 years.