Vodacom is robbing me

Vodacom is robbing me I had cancelled my LTE contract with Vodacom due to the fact that they could not deliver good speeds my area Overport Durban. I had requested to cancel for this reason. At the time of cancelling they didn even try to retain me as a customer and try to resolve the issue. They just cancelled n I had like 3 days to find another ISP. Now they are saying I must pay R9000 for the remainder of the contract. How ridiculous is that as I already signed another contract and now I can't afford to pay this. When I email, they want all the proof for the queries raised for the low speeds. After providing all the information l, they just go quiet. When you call them, they just push you from pillar to post but no 1 bothers to take the initiative to try and resolve the issue.