Capitec credit card

Im done with this bank. I keep on paying my credit card each month...and they keep on saying im in arrears. Ive emailed all my pop's to them and last year Dec the bank transferred my payment made to my loan account that was paid up in July 2017 to my credit card. I received this sms this morning...Capitec: MS BENZIN, a Section 129 letter of notice has been posted in terms of the National Credit Act. Call *** to avoid legal action.

I keep on emailing them with proof ext but still they keep on treting me with these sms.

What can I do because they make me look like a bad payer!!!!