Go to the BIS site on your computer and have Service books sent. Then do a master reset. All should be good and you will get your registration message. While there check your PIN in the "Change Handheld" area, customer service may have put in the wrong PIN.
Next time you can do this all yourself. You simply can go to this site and change your IMEI and PIN, send service books. Or course you need to switch SIM cards but customer service is not required for any of this. I have done it many times with no problems.