BofA will Not Let You pay Extra Principle

B of A carries a loan from one of my vehicles. I like to pay off my vehicles early, so I often add an additional principle payment to my monthly payment. B of A refuses to apply that payment to the principle unless I send them a check - you know, like back in the last milennia. They apply it to future interest payments, thereby keeping the very most amount of principle intact. I have called them numerous times and it takes up to an hour to get them to apply it properly. This is just dirty and rotten and money-grubbing. Don't use these folks, they're terrible and hate their customers.