Incapable staff

I have a loan with the bank, everything is been running smoothly until the bank decided to change the debit order from the 28th to the 26th for what reason only God knows. I get paid in the 28th and they know that because I bank with them. They have been treating legal actions against me since the 26th. Yesterday the 28th they got their money but I still get phone calls and messages treating to hand me over. The staff there seems to be incapable of resolving their system errors. The staff is very ***********.