Poor customer service

Just spent lunch break at Cell C shop in Hemingways Mall East London. VERY DISSAPOINTING. Went to cancel my contract which has expired. Cannot cancel in shop. Can only take out new contract. Assistant called some helpline where i spoke to very cheaky Yvette. When i could not tell her were i worked when i took out contract BECAUSE I COULD NOT REMEMBER HOW MANY YEARS I HAD THE CONTRACT she told me i had failed security check. I asked her to tell me when the contract was started then i would be able to tell her she refused. This after giving her my cell number, id number, home address and which bank acount gets debited in front of five other people standing in the shop. Now i see all these complaints on web and realise why they won't cancel in shop. IT'S TOO EASY.