African bank.. a red tape python..

African Bank; settled a loan with African Bank three weeks ago. They deducted money again. I jumped on the only contact point available on all the electronic platforms. Jumped through many hoops to get to an agent.. Was told that my telephone number.. the same one I used for applying for the loan.. and the same number I called from was no longer valid. I need to go to a branch now to fix this before I can find out why they deducted money again. All I want to know is why they deducted more money after receiving the full settled amount for a loan. They cannot do any other security verification with me. All other banks can ask security questions...PS I was required to punch in my ID no before getting to an agent. I had to confirm my ID number telephonically before being told I must go to branch because they cannot send me a whatsapp..