Debit oder payment date query

I am so disappointed with budget insurance. My debit order is for the 5th but there was no money in my account yesterday to process the debit order. Someone deposited money today the 6th in my account and they took it. I went to my bank so that they can reverse the transaction but they couldn't because of Debi check, they advised me to contact budget so that they could reverse the transaction. I did contact budget and they told me a stupid reason that they can't reverse the transaction because I have a contract with them. My argument is that the debit is for the 5th not the 6th, why are they debiting my account on the 6th because that is not my debit order date. This is not the 1st time of them doing this. Even if there is no money on the 5th but on the 10th you have money they still debit. This is *******, refund my money and cancel my policy. Other companies don't do that, if there is no money on the date of debit they don't take money the following day. You have just lost a client and believe me word of mouth is very powerful. I am going to discourage everyone I know not to use you.