Contract not stopped

Hi my name is Branden Faroa and i had sign a contract with Cell c at Game stores in Parrow Cape Town as the promotion was for 24 months.I however did pay my contract finish from December 2006 untill December 2008.I got a call yesterday and they actually send me a statement from DMC for an account of R3 148.80 on 16 March 2016.I need to get this matter sorted.I cant apply for my Homeloan.My ID number is ***.I cannot afford my name to be listed and this over the fact that Cell C just went on charging me for months and i sighned for 24 months.I now need to pay them atleast R1500 with discount given said the consultant that send me the mail to have it sorted.This is a mess they caused 8 years ago because no one told me I must write a letter to cancel in store and I sighned for the promotion.I never took an upgrade or enjoy the benifit of the contract after the 24 month period.my cell number is ***.this need to be taken care of or be stopped cause this is not how you do bussiness.They tell you in the shop that it will be a premuim for 24 months not for a lifetime or till whenever.Please hello Peter I need your help and assistance.