Forced to have two contracts

I am incredibly upset with Vodacom. After being a loyal customer for many years I have realized that they honestly just do not care. Over a year ago I went to the vodacom website to do my upgrade. I have been doing the upgrade online now for many years. I thought it all went smoothly until I found out that Vodacom was overcharging me. When I went to find out why they proceeded to tell me that instead of an upgrade I actually signed up for another contract with a new number. This totally shocked me because there is no way I would've done that, why would I need two contracts with two numbers? Firstly I do not make much money and would never afford two contracts.

After numerous phone calls to rectify this the only solution I had apparently was to downgrade my one contract and keep paying off the other contract until it ends. I had to accept this otherwise I would be paying a fortune each month that I just cannot afford. I log in to my vodacom account now to discover that I am in arears of over R630. I just find this incredibly unfair as I know I was not in the wrong.