ok i hope this works for you but it worked for me !!
this is legendary!
i say it now because i didnt now the method but i found that mail back so...
Goodluck
"Cancel your billing plan, wait till your acct is frozen, add a payment method it will be active for playing straight away, go in game play, minimize game, then cancel payment method, no payment should be taken and you can still play wow. I've been doin this for a year(until my account got banned for scamming accounts).