What does the contract with your bank say about post dated cheques? It should be stated someplace.
Banks will cash cheques without looking at the date as they only look at the amount, the security details at the bottom and for your signature. The CRT assumes if you are sending them a cheque to pay something, then you must have the money in your account to pay it.
A cheque is a bill of exchange payable on demand. If it is PD, then it is no longer a cheque. That is why the CRT cannot hold it.
If the CRT were to cash your cheque and it bounced, then you probably pay a fee for that, but read your contract with your bank for those charges.
Live and learn I guess, but it is not the CRT's fault.