You may try to go back to the store that helped you. There are 2 numbers for Customer Service. From your phone 611 (Customer Service), from a landline 1-800-866-2453. For the 611 number use the option TROUBLESHOOTING. Things happen, especially gremlins. Welcome to T-Mobile. I have had no regrets coming here when I left AT&T after 14+ years.
We love hearing folks decide to join the T-Mobile family and we certainly want you services working ASAP. Are you still waiting on getting access to your account? If you're getting an error message, can you let us know what it is?