Brooks & Luyt collection without validation of debt

Received numerous sms's about monies owing to MTN (which i confirmed via email with MTN twice, i did not owe them anything), after several calls to Brooks and Luyt (which also acted as Nudebt and CSS MTN Lawyers) to please send me the validation/confirmation/origin of the debt, no results. still kept on receiving sms's to threaten me to make payment , but no validation of debt....? have not had a contract with MTN for several years now........ don't know where this debt is suddenly coming from?