Over charging and Bad business conduct

I paid the above mentioned debt collectors what was due to them an amount R4 700 on 17/11/2018 using all the details (bank account no., reference no., and bank account ref: no.) To my surprise, on 31/05/2018, I got their sms demanding payment of R4 700 + interest = R5 830. I went to their offices and gave them my bank statement to prove that I have paid what was due to them last year and I used the correct reference no. which is reflected on my bank statement. To my surprise they claimed that I used the wrong reference no. and I'm liable to pay the difference because they claim that they've been struggling to get hold of me. Now they threaten me that they will repossess some of my assets should I fail to pay them R1 150. I went to my bank to explain my situation and my bank had a proof that I used the correct details and this company has no right to intimidate me and to force me to pay. The lady who works in their offices then chased me out of their offices and the business owner, Mr Scheepers was not professional at all because he didn't want to listen to me and was verbally abusive. The only lady who calmed the situation is a lady by the name of Engela who advised me to go to my bank (Nedbank) to seek proof, which I did and Nedbank phoned and spoke to them. But to my surprise, after a week, I got their letter still demanding payment.

I therefore seek assistance from you as I feel aggrieved since this company treated me unfairly.

Kind regards;

Sello Mafela