I messed up while changing my name so how can I get another one if possible?

You will unlock a few more as you play. I'm sure there is an exchange store you can buy th but I checked and cannot find it. Keep an eye out in the event exchange stores and perhaps Sometimes you can purchase it from there. Sorry I couldn't be more help.

Ooooh I found it. If you click on mansion, then Mall near the bottom right of the screen and click items you can buy a new rename card for 200 ignot.