Radio lock did not set code?

Transmission was replaced on vehicle a while back. I had not driven car much as it was shortly before illness. Now I realize radio is locked. We did not set code don't know if dealership did. I called dealership (as they replaced Transmission) and have been told I have to bring it in and they will fix for$300. That is stupid. I have a Honda I founf a number I gave them the vin and they gave me the code. I have done what research I can and found the "scrambled code". GM still wants to charge for code. Is there a way just to get my stupid code? Also once in the LOCK mode how do I get it back to ---- to put in new code. I'm rather frustrated. I have a nice sterio, it would be nice to be able to listen to it. Thanks!