If you want to keep your number, contact AT&T support right away and ask them to temporarily re-activate your account so that you can get a transfer PIN. They may be able to help you, especially ...

You can call customer service by dialing *611 from your Metro by T‑Mobile phone. If you don't have it handy, dial 888-8-METRO-8 (888-863-8768) from another phone. Get your transfer PIN by ...

Have a Motorola phone? Want to make it more secure? This secret PIN Scramble feature lets you do precisely that.