Need to stop autopay now. Changed payment method

Hello

I changed my autopay payment method yesterday Sept 2.  I need to use this new payment method for this bill September 4.  I cannot get a human representative to talk with me.  I did autopay by phone.  It was the best I could do.  But my payment WILL NOT go through if it is the old method.  I did receive an email stating everything was updated but that the new payment method would not be taken until next month October that is way too late can someone please contact me