I filed an extension on my state return (Oklahoma) but now Im unable to pay the amount scheduled to come out of my bank account. How do I cancel that scheduled payment?

I suggest you try to contact the Oklahoma DOR

If you are looking to contact an elected official or a particular agency or state office, refer to the list below as needed or view a complete listing of all state agencies. 

List of Department of Revenue by state  List of state DOR's

I called them and they said they cant do anything and to check with turbo tax to see if they can cancel it. or go to my back and put a stop payment on it.

TurboTax just transmits the returns, we don't deal with money. The federal government can stop a payment so it is interesting that OK could not. That leaves the last option, contact your bank.