Yes I can't believe it either! Not only that they didn't accept it but they said that the statements do not proof that the money came out of my account.. well... unless the bank is showing the transactions made by another person in my bank statement is hard not to believe that the money went out of my account.
In any case, they need to send me the supporting documents for the claim which I know they don't have, otherwise how can they claim I did or did not pay?
I've sent a copy to the lease advisory service so they can confirm whether the service charges are considered as rent or not. With this I will have more of a defence if I can't get by bank's info on the cheques.