Horrible customer service and account management

My Fiance took out a contract with MTN at the Glen branch for 2 x Lenovo Yoga 2 8 inch tablets with 2gb of data for R249,99 per month each. The lady told us if there should be anything wrong with the tablets we should return them in the next 7 days. The two tablets had a screen fault in the bottom corner and we returned them after 4 days to MTN the Glen where they assured us that they will be replaced, at that moment they did not have stock of the tablets and they will contact us if they have stock. They phoned us one week later and told us the tablets will be sent to lenovo and a week after that it was sent to lenovo, then they said no its going to be repaired. My Fiance asked them to cancel the contracts as she waited too long for feedback on the tablets and the constant changing stories. They cancelled the contract and then they told us they will send us a credit note as she paid for it already. Till this day no credit note was issued and she is still paying for the tablets which she does not have and the sims are cancelled too. We are paying for something we do not have and we require feedback asap or we will feel the need to contact Carte Blanche, the newspapers and ombudsman