I think I am going to regret going with them....

I tried to get in contact by calling, eventually after the 5th time i got an answer but the person could not help me. I told him that the debit order is set to go off on the 21st but that is the day I get paid, it is not to day the money will be in that day, and I am not going to stand for bank charges for not enough funds for when they want to deduct it, I would like to have it go of the 22nd (when I usually see the money in my bank), he continued to say the same thing that the company has policy and it cannot be changed - although I did input that I would like it to go off the 1st when I completed the document. I sent an email on 6 June 2025 and still nothing. Now I got an email saying the interest rate is going down, but my premium is now higher, how does that work?? It is going to go off the 21st of June for the first time, but I am already paying more than my agreed premium?