T-Mobile Sim Unlock??? Is there no workaround?

[dl8806]

Soooo I have a N20U via T-Mobile and obtained a Sim Network Unlock code. Tried to use another carrier's sim card to enter the unlock code when prompted and was directed to the Network Unlock in the Mobile Network settings. I chose permanent unlock but T-Mobile wasn't going lol. Denied! Is there not a way around this to sim unlock the phone without going through T-Mobile??

Thanks for the help