Jet unable to resolve payments issue

I have retail account with Jet of which I am a good payer for over 10 years. In June I received an email stating that payment for May was not received and I emailed them proof of payment. They rep**** to my email saying I have to get target details from my bank because they didn't receive the payment. I wont go that route as we are in the middle of a pandemic and the proof of payment from my bank was proof enough that payment was made. Now I receive call from their collection department every day twice a day and I have to repeat the same story to different people. Will jet please resolve this issue as I am now nervous to make payments to an account they suddenly deny receiving my payments in. I have emailed *** and *** I even sent whatsapp to the number they gave me ***.