Not helping with upgrade or cancellation. Stuck with a useless contract!!!!

I have been trying to cancel a Cell C contract since the previous week. I called their call center and after answering all the security questionnaire I was told I had to be transferred to the cancellations department at 084143 option 2. The call suddenly dropped and I was unable to request the cancellation. Then I went to Cell C in Menlyn and after being treated very rudely by the agents they told me I had to call the same number. Every time I dial this number I get a recording that says the number does not exist. Cell C is treating me very badly, after being a loyal customer for 2 years. I tried to upgrade, but they forgot to do something on the system. Now I have been charged the full amount for this month, but Cell C is only giving me half of the data I normally used to get. Cell C refuses to give me the data according to what we agreed and spoke through the phone with the upgrade agents. Cell C is making it impossible for me to move forward. The upgrade was not done, the cancellation is not possible via phone or at the branches.