TRYING TO CANCEL ACCOUNT RIGHT

I wish to cancel my MYOB Account right immediately - the software and website are hit and miss at the best of times. I wish to update my credit card details so I can pay the last month which is owing HOWEVER the portal will not accept any of the credit cards saying "payment cannot be processed at this time." This is after it took forever to log-in in the first place, when I kept getting the message:

https://login.myob.com/oauth2/logout?client_id=622d673c-610a-4a5a-9bfb-abe61e939039&post_logout_redirect_uri=https%3a%2f%2fmy.myob.com.au%2fpages%2flogin.aspx

PLEASE tell me what is wrong so I can pay and CANCEL.