Legal Action threatened due to non-payment

I have an American Express Credit Card with Nedbank. I did not make the minimum payments for a period of time but did start to at least pay something since July 2015 this year. I have made 4 payments since then. When I was not paying I was constantly threatened by SMS with visits from the sheriff of the court even though this is a contravention of the national credit act. I did not make any complaints as I understand I was not paying anything. Since I started paying I have received no acknowledgement of payment and no contact of any kind. Until today when I received an SMS stating the following - Dear Ms Greyling. Please note that your Nedbank Nedbank Credit Card A account will be HANDED OVER to an Attorney for LEGAL ACTION. Contact *** urgently to STOP LEGAL ACTION and aditional legal costs. Ref CCA140276 - I understand that I might not be paying the minimum the bank wants me to pay but I am paying what I can afford. Rather than even acknowledging the payment, I get threatening SMS messages indicating that my account has been handed over, why should I continue paying if my trying to at least pay something still results in me being handed over to an attorney and more costs.