Eeek, shadowsplashx12! That's terribly inconvenient - I can't imagine what the trouble could be, but we definitely want to get this worked out for you so that you can use your device with whatever SIM you need to.
How long ago did you receive the e-mail confirmation? I know you have to wait 24 hours from the confirmation's arrival before you can attempt the steps. If this timeline has already passed and you're still having trouble simply inserting the non-T-Mobile SIM, we'd need to make sure you're completing these steps:
1. Back up using iTunes
2. Erase your iPhone
3. When you see the Welcome screen, connect your device to iTunes
If that's still not successful, we need to take a look at the IMEI and unlock request on our side to make sure everything was handled correctly. Since the Support Community is a user forum, we're not able to review that information here - can you please Contact Us so that we can iron this out for you? Please keep us posted!