Angry Customer needs answers!

I have a contract with Cell C I have requested for them to change my contract from 36 months to 24 months however this has not been done from last year I have been calling continuously and still nothing, I have been getting told this will be sorted however it is still in a pending status I am gutted by this as I have been a loyal customer and this has happened before where the agent misled me I brought it to the companies attention still nothing! This month I was double debited. Can this be looked into I’m not happy with the service I have been receiving . This is the reference number that was given to me-***.

Your help will be highly appreciated!