charging me for a service I do not recieve

i have been querying the over charge on my bill since march 2015. it appears i have been paying for BIS for my Samsung because Vanessa forgot to cancel it even though i was took a new contract when my Blackberry one matured .I have been given a different excuse each time. I first spoke with Vanessa Naidoo and she said she would sort it out. Nothing changed. Spoke to Ronnel she promised to get back to me > nothing . I phoned customer care and spoke to Faizeel Rugan who promised to sort it out and email me . He did stop the Bis but not heard another word regarding refund. I went to the branch again and Ronnel promised the owner Shamaal would have a reply for me within 48 hours. That was on !8th Dec and nothing from him either. Clearly these people do not care and have no intention of sorting anything out.they change excuses as to why they cant help and acutally blamed this whole mess on me . The final straw was that Vanessa actually slammed the phone down on me yesterday rather than sort it out once and for all.