Do your job properly... Not just threats threats and more threats!

When I first received my call, I explained my situation and we came to an agreement... Every month I paid what I had and I would email the proof of payment. When I was close to making the full amount that they asked in the beginning, I got a funny feeling and asked for a statement. For two months I asked for statements with no success. Finally I got the statement and guess what??? They did not pick up on all the payments made and threatening to take legal action. I got proof of payments again, costing me more money and emailed through to two different emails and requesting in getting a proper statement and to rethink the interest because they are not doing their job properly. Three weeks pass and I get another threatening sms stating they will take legal action if I don't pay R599... But I know that all I owe is R80.... And yet again, no statement, they have not looked at my proof of payments and still threatening me!