Subscription increase

I have 5 contracts with Vodacom and a loyal subscriber for over 20 years! I refuse to pay the increase in subscription as I upgraded 2 of my contracts late last year at an agreed subscription rate. How do you just increase it a couple of months later? I will not be renewing any further contracts with Vodacom as I find this totally unacceptable especially that the letter states... Vodacom has worked to increase the speed, quality and breadth of mobile coverage in South Africa... What utter *******! I have laid a complaint about the coverage in my area for the last 5 years and keep getting told they are working on upgrading it. So no i will not continue with Vodacom as not even a technician has been out here to check the coverage in my area but it's ok for you to increase my subscription rates.. Whatever! Fine print blah blah