Harrasment from agents and systems of MBD

I had difficulties with the system and the agents as to how they operate.I manage to settle my accounts which were handed over to MBD . On the 25 of September 2020 we arranged a discount for a settlement and i made an online payment and the agent asked a proof of payment and it was granted . I was told then by the agent that the payment will take 7 days to reflect .To my surprise i was getting sms and phone calls asking me to pay. Even my wife was also getting calls and SMS . I will be asked every time to send proof of payment .This is so frustrating now as to how many agents and managers must I email the proof of payment.On the 01 October 2020 I was told that a payment was received , few minutes after that even today I'm still receiving calls and SMS to settle the account . Now I don't know what to do to stop this irritating treatment .I call the agent who told me the payment was received she told me to ignore them ,I told her that my wife is also receiving the SMS and calls so she is beginning to doubt that either I made a payment to the wrong account holder or ********** . The other thing is that this Loans were more than 5 year old . Can anybody advise in this matter please .