Hi everyone, I just discover this game and it's sounds amazing ! I just beat the tutorial, and the game ask me to create an account. Since I already have my Pokemon Club account for several Pokemon game on DS and Pokemon GO, I want to use it. But when I put my information this window pop-up

For those how doesnt speak french it's roughly translate too : You can't go to a full account with an existing account. To have a full account, please create a new one.

What should I do since I don't really want to make a new one since mine is existing for years now !

I'm sorry for the noobish question but I didn't find anything about this issue..

Thanks