Why have a contract?

Recently advised by Vodacom that my monthly subscription will increase by R10.00 - not a lot of money but the principle. Sent 2 e mails - automatic response to both with reference number - as well as 2 call me, facility from their website. Tried to phone the help line but gave up after 6 minutes with no reply. No response to date. If their T's and C's state they can increase subscription at will half way through the contract but I cannot cancel with severe penalties, what benefit is there in have a contract? <br> <br> What if the increase was significantly higher than R 10.00 and how many other subscribers are in the same situation? I have been a client of theirs for some 25 years.<br> <br> They do not even afford you the courtesy of phoning you as promised on the website.