Thoroughly annoyed

Their call center is useless they will send you from pillar to post. My contract expired on the 28th of August, I had previously asked to be migrated to a different plan but received no assistance. They said someone would call me back. When the contract started I was paying R269 monthly, then in April there was an increase and I was paying R278. The latest invoice they sent me shows that I must pay R718 for the exact same product that I have been receiving all along. I’ve called in twice to try and cancel my contract and each time I’m told there are system issues. Customer service is very poor, agents don’t take the time to understand what you are asking them. Flabbergasted at the treatment I received when I’ve been an excellent paying customer for the past two years. Is it even legal to have such a significant increase in a price with no explanation whatsoever? I asked to be migrated to a different month to month plan of R249, they even sent me an email saying they would migrate me and I didn’t need to do anything on my side. Now I’m receiving invoices with exorbitant amounts of money. R646 For 30 gigs of data? In this economy?