Logged into Game Center, but it isn't working?

I recently downloaded a game(Battle Bay) on my iPad and had to create a Game Center account to play it. So, I get a phone and sign into that Game Center account, then download the game. I do the intro demo for the game that you usually have to do before you sign in, but this is where it gets weird. You can use your Game Center account name or create a new nickname for the game. So, it automatically puts in my Game Center name(SloloLegend) and gives me the option to change it, but when I press continue it says that the name is already taken. Do I need to do something to further pair the game with my account? The fact that it automatically put in SloloLegend should hint that it's paired enough. Can I not have it on multiple devices? -Slolo