What would be an adequate reason to cancel a Contract with Vodacom?

On promotion I took out a Vodacom internet contract and from day one
I had nothing but trouble with them.

They have changed my contract. I had no say in the new terms basically
I was contractually raped.

My net is slow and downloads fail constantly.

I cannot use Skype as intended.

Despite the fact that there are 4 large Vodacom branches not 1 can
offer direct technical assistance. They phone the same numbers
customers uses.

If I cancel why do I lose the data I paid for?

How can the consumer Protection Act help me to stop this


Thanks!!!