Bank Statement not enough proof of payment

Dear MBD, getting pretty fed-up with your non-response to my e-mails. I've had to go as far as to send you my bank statement as (Proof of payment) as your "competent" finance department could not track my payment after I made payment whilst your call Centre assistant took me through the payment process. List of people not responding to my e-mails as I've requested a "PAID UP LETTER" , ***, Euginia Zondo <***>, *** *** ***

Please tell me how to we proceed from here on going forward ??