Vodacom - this is not right!

I am so angry - I was due to upgrade my phone last year and decided not to as it was still working fine - I called Vodacom to see if it was ok to not do the upgrade and do it as and when necessary. They said it was fine and suggested a cheaper contract which obviously I took. It was not explained to me that then I would be tied into a 24 month contract (as it was "migrated") and wouldn't be able to then upgrade my phone for another 2 years! This is what I called them about and was trying to avoid otherwise I would've upgraded the phone then and there. I now sit with an old phone which is slow and the battery lasts 5 mins and I can do nothing until Sep next year - this is ludicrous VODACOM. How can you do this??? I have lost all faith in Vodacom! Now I am stuck in a contract I can't cancel and a phone I can't use - THANK YOU SO MUCH VODACOM!