Changing name

I can't seem to find an answer anywhere so I figured I'd try here.

I recently deleted a bunch of emails, one of which was connected to my Google Play account. I signed in with a different email and made my Gamer ID. It worked with one game but on another it has my name as 'Charredcop1238' or something like that. When I press the menu button, the proper ID and email address is listed but when I sign into games it's the autogenerated one that appears. When I go to change the name, it says the ID has already been taken. My game progress is still fine, I just want my proper ID. When I go to change the ID it suggests adding a number to make it different than the used ID name. I'm the one who's using It! If I do decide to add a number, will I have another ID? Why has the name changed and how can I get rid of the autogenerated name for good?