Complaint logged for Sim never received since inception and mono no response on car disk

Where do i start. Wether I call or visit an mtn outlet I get no joy. I have logged complaints it's closed but nobody even calls. Such disrespect for customers. More than 20 years I have used you as a provider never defaulted once but this is the ********* behavior being portrayed towards me. When logging in my my mtn I noticed a Sim on another's name I was perplexed because of the Poppi Act and asked if be removed I was told it's my Sim of the contract I renewed its the Sim I received with the free phone huwai nova 8i. I never gof the Sim or the data since inception.