Telkom and sms lawyers

Without notice I was apparently handed over to DC Fourie attorneys, after I closed my account, whilst waiting for a final bill. I phoned Telkom and was told I could pay directly (as there is no way I am going to pay any monies in response to an unsolicited sms) Now these sms lawyers send me another sms telling me I must pay them or I will not be removed from the credit bureau listing. Is demanding funds and listing me by sms even legal? What kind of lawyers do business by sms? How can Telkom be in business with such unproffesional businesses?