Billing error due to store

Please could you assist. I am a telkom customer in Strand, Cape Town. I am struggling to correct my account, as i am being billed for 2 contracts due to a error the store in Somerset Mall made.

I called the help desk and was advised that the store has to log a call to confirm that they opened a new contract for me because their systems that day could not do upgrades.

I waited for 7 months for that upgrade as the store people told me I had to wait for technicians. When I finally got the upgrade the lady told me that the system would not allow her to do that and I had to go with a new contract. When I queried my account, I was told that my old contract was never cancelled by the store and I am mow paying for 2 contracts. I've been contacting the store for the whole week and they find enjoyment in humiliating customers by not answering phones and treating customers with disdain.