这个比Tmo的差太多了：
previously had active wireless service from a competing wireless provider for a min. of 120 days
new line must remain active for minimum of 60 days from activation.
If new port-in line of service is cancelled within 12 months of activation or become ineligible, AT&T may charge back the full value of the AT&T Visa Reward Card on final bill and will not be able to reactivate the line of service or have the charge removed.
一方面说保持60天，一方面12月内cancel的话charge back。。