Why can't TFG reverse interest when their website/app let them and myself down

I made a payment on 25/02/26 on the bash app. When I bought electricity on my banking app; I noticed the payment was still not cleared on their side. I couldn't contact them immediately because it was on a Sunday. So I contacted them the Monday morning. I was told I should contact my bank which I did and I was advised that the merchant has to apply the payment on their side. I contacted TFG again and was told that they do have glitches on their app sometimes and that it does happen. She told me that I need to wait a few days to see where the money went. I did but called again and then I was told to ask my bank to reverse the payment because they couldn't find it apparently. I do my payments every month at the same time and it was only TFG that was still not cleared. I then made a new payment inside a branch and then I had to ask the bank to reverse the 1st payment. My problem is why should I have to pay interest if I was not at fault. I told them that they can check my profile and they will see that I never skip or make late payments. Why should I be charged interest because of their faulty system. They even told me that I must remove the banking details I have on my side. How can I remove banking details if I never had it. I just pay it through their bash app. Unbelievable and unacceptable😡😡😡 Felicia