Displeased with African bank call back

African Bank phoned me about my review and i stated why i was unhappy with them, now they want proof that transpired 6 years ago, how must i get that if all was done via telephonic conversation between myself and African bank, the proof via bank statements i can get but African bank needs to do their work and look at 6 years ago statements before taking every month money off my account which to me is *****.