"renew your justified lack of faith in our company"

Last month I rented a car from FirstCarRental, when my car went in for an unscheduled electrical check. I chose them simply because they were the closest to my office, hence easy to get to. The rental itself was painless; but after returning, I was charged for additional damages. Upon further investigation, I found that they had charged another client's damages to my account - and it took almost 4 weeks (!) to get my money refunded; and that was after a particularly nasty email was sent since polite emails, phone calls and even rocking up at the office twice didn't have any effect.

In the last email, which was very appologetic (though they didn't even pay me my interest on the overcharge), I came across the following line:

"I trust that you will allow us to be of service to you again in the future so that we may have the opportunity to renew your justified lack of faith in our company."

Really? I should try them again, so that they can renew my already low opinion of their services?