********* forced to pay more than the invoice amount

Would have received 0 stars if possible, I recently bought a vehicle from them. I told the salesman that it would be a cash buy,. I was invoiced and made the payment according to the invoice(documentation fee added to the vehicle amount). The vehicle was not released as they wanted an additional 10% for "bank fees" that was not invoiced. This is the first time I have been asked to pay more than an invoiced amount. The manager was rude and insisted in this additional payment saying that they will not even refund me my total amount for an agreement of sale that they broke. Since when does the customer pay for the operational running costs of a business(bank fees)? What is next with them, will they ask me to pay part of their rent and electricity for visiting their showrooms? I find this totally unacceptable how I was "*********ed" to pay an additional amount after the agreement of sale as the vehicle transporting costs have already been paid by myself. They have no ethics. An agreement of sale is supposed to be, exactly that. I have complained to their "customer care" department will be taking this mater further.