Contract cancellation

I had a contract with Vodacom for 2 years which was due to end on the 31st April this year. A Vodacom consultant called and asked me to upgrade I told them that I am not interested anymore. The lady I spoke to then offered me more data (hundred gig day +50 gig and hundred at night) if I choose to take up a new contract with them and I agreed to do that only to find out that the contract they gave me was a home connector that I had to pay out of my own pocket. I discovered that my sim card had no network and have been trying to contact Vodacom since the 1st to cancel my contract with no assistance. I’m afraid to dispute and cancel the debit order as I know of the negative impact it will have in my credit record.