We recently ported our numbers from T-Mobile to Sprint, and then to AT&T all within a couple of weeks. We had a bad experience with Sprint, and bailed to AT&T after one week. We initially ported our number from T-Mobile on 10/14/11, but T-Mobile still charged for services through the remainder of our billing cycle which went to 11/06/11. Apparently, it is a common practice for wireless carriers to continue to charge you for services that you are not using when you port your number (because porting your number effectively cancels your service with a wireless carrier). Even though you cancel your service (we were on a month-to-month contract with T-Mobile and otherwise paid no early termination fees), the last bill is not prorated. T-Mobile does it, Sprint does it, Verizon does it, AT&T does it (although I could not specifically find it in their lengthy wireless customer agreement), and I'm sure every other wireless carrier does as well.
I was unaware of and annoyed by this sneaky little arrangement which is definitely spelled out in the T-Mobile terms and conditions. No one wants to pay two full cell phone bills in one month, even though you are effectively only using one carrier at a time. I'm not aware of too many other services where canceling your service doesn't result in a prorated final bill (maybe gym memberships?). How is the wireless industry able to do this? Indeed, the world still asks how they are able to keep charging so much for the quaint, old service we call text messaging when it only consumes 160 bytes of data. I suppose it's their way of recouping the costs of number porting. When I spoke to a T-Mobile representative about it, I got reprimanded that I should have read the terms and conditions more carefully.
UPDATE 11/16/11: Today I received our final bill from Sprint for the 7 days we were with them: $230. Ouch! Yes, $230 for 7 days of miserable Sprint service, during which time we dropped 99% of all voice calls and got only 1 bar of signal at my house and averaged data speeds of about 500kbps. The bill was originally $245, but they erroneously began charging me for Sprint service from October 11, even though our iPhone 4S phones didn't show up at our house and get activated until October 14. There is something morally wrong with the wireless industry forcing consumers into such anti-competitive agreements that discourage subscribers from switching mobile carriers, and continuing to charge for service when no service is actually being used by the consumer.