That is bullshit actually. Go to Mog Station and double check to be sure that the account is indeed suspended:
https://secure.square-enix.com/accou...est=mogstation

If it is, the only thing you can do at this point is either reach customer support via chat or phone and have them lift the suspension from the account. You can find the support information here:

https://support.na.square-enix.com/c...Password-Chat2

Good luck!