How do I get the unlock code for my device? I already sent the fax of the receipt

Hello,

I recently for a Samsung Galaxy S3 from a T-Mobile store in Harvard Square, Cambridge, MA.

I was told I can fax the receipt to receive the unlock code and I did the same. But I haven't got the unlock code or in fact, not even a reply of any kind from T-Mobile. I had also included a cover letter along with the receipt indicating my email address and contact details.

Can someone (or T-Mobile support) let me know how can I get the unlock code for my device? I would like to have this code ASAP.

Thanks in advance.