Terrible service - quick sales and then no response!!

I have had truly terrible service from MTN through one of their agencies. I have been a customer with them for more than 25 years and had an ongoing contract. On Tuesday 7th August 2018, I was contacted by a sales agent to upgrade my contract. I said to her that I want a contract with a new handset (which is coming out later this month). The consultant swept over my comments. I agreed to a new contract but was told I could cancel within 5 days. I have been trying ever since to cancel this contract. I HAD every intention of continuing my contract with them but wanted to make sure I was on the best package for myself. After being verty efficient to send me an (MTN) contract, MTN has not been able to help me to cancel this upgrade - I have been given many incorrect numbers of people who cannot help me and when I was transferred on the line to the companion organisation - it seems to have been to some kind of recruitment agency who did not answer the call (I had originally phoned ********** 667). I am disgusted that after being such a loyal customer you are treating me like this, (Reference number is # ********** 4. I am disgusted with this service and angry at the extreme lack of interest once you have sold a contract and conveniently unavailable when I need to cancel. I need a response from an MTN representative as soon as posisble or will be approaching the OMBUD.