terrible services

Most terrible and unprofessional service ever. I paid up my jet account and forward a paid up letter received from EDCON . Now all of a sudden after 5 years they start to harras me non stop again for the same account. i forwarded them again the paid up letter but no!!!!! they want the actual proof of payment. i mean same was paid more than 5 years ago!!!!! but they insist on the proof of payment and not the actual paid up letter .