Constantly lowering interest rates
I opened my TSB account very recently and they are already lowering the interest rate. Because of the fact that it's an account where you'll be penalised for taking out your money, I'm now gonna miss out on the interest for however long because I now need to move my money out of that account into a new ISA, because they're absolutely incompetent who just can't leave things the way they are. I just opened the account and you lower the interest rate immediately. That is the most frustrating thing.