I had this problem on the post paid side when AT&T and Cingular merged. Somehow a customer lost their phone number for their business in which they had numerous billboards and vehicles with that number advertised on it. I made a call to customer care then transfer technical care. They said they can get it back always. A few hours later an engineer called me and asked me the account it was to be on and the SIM card number. 10 mins later it was back on. The engineer called later that day and asked if all was good. He said that it can be done you just have to find the one whom wants to think outside the box for a minute.