Im having this problem too. Its saying that its already registered, but its registered to me. Down below is a list of EA games and the name im trying to switch back to is used for all of them....
If that is the case @slicky1019 then you will need to use a different username. The easiest way to fix this issue can be by playing around with the spelling or adding numbers at the end of the name.
I’m having trouble with changing my username. I really just would like to change it. I’m doing this on my phone and the whole website is just confusing.