Urgent cancellation

I am very disappointed at Telkom, I am paying R199 monthly for 80 gigs during the day 80 at night, but I suspect I am getting less then what I am paying for. My data only last 1 and half week. I want to cancel my contract with immediate effect, I was told to dial 081180 or log on to my Telkom portal I did all that but it doesn’t lead me anywhere. Please help me with a cancellation I am aware of penalties I don’t mind paying them!!