Refund me, Ford Credit.

My spouse contacted Ford Credit for a Settlement on my Ford Everest. She was given the settlement and paid the full amount before the cut off date, giving more than enough time to show in Ford Credit bank account (and basically my Cars account). A few days later we received a message that we need to pay in a further amount otherwise the account will not be settled. We found this strange but nevertheless paid the amount. Receiving a payment history now shows that we are indeed in credit, which is correct. Requesting a refund has been fruitless. We get emails back that the amount has been written off... how can you write my money off??? This is leaving a biter taste in my mouth regarding Ford Credit so that I am now not even considering purchasing another Ford never mind the use of Ford Credit! This is coming from myself that currently has two Ford vehicles and have been driving Ford since 1989... our paths are about to separate due to the reason above.