Duplication on account and unwillingness to cancel

a secondary account was opened when I took out Cellphone contract with Cell C. it is 2 years now and still the 2nd account is not cancelled from my name and is reflecting with credit bereau as bad payer due to a mistake made by a consultant and investigation found mistake, BUT still it is on my name and management does not phone back, irrelevant of how many messages I leave to get this sorted out. this hsa been a nightmare that never ends and I am unable to move service provider, due to my bad credit record which was caused by this company who cannot sort out their own house with accounts and duplications thereoff when you apply for a contract. every person i meet, I tell about this bad service and will continue to do so into the future as this is a monthly reminder on my account with Cell C.