Misleading infomation

Our car was a write off, insurence paid, however there was a fall short. Which we later received an email stating that we will be paying a certain amount effect of 30/10 however that was not the case as they debited the initial agreement. When inquiring I'm told the calculation were done and the money that's debited was already sent to the bank and has already been deducted from the short fall amount. Which does not make sense, how do you give a customer a figure based on the money that has not yet been paid. I'm now told the the effective date of the amount received on the email in November, when I refer them back to the email they sent, I'm told it was a misunderstanding. Question is how is it a misunderstanding when they do the calculations and send am email to customers. I don't want to touch on how you cannot get ahold of their customer service.