Worst Customer Service: False Offers

Good Day, again I write about Vodacom's poor service to say the least. 2 months ago i tried to cancel my contract. The lady offered me a much lower deal.She said that it would be sad to see such a long term client of theirs cancel and they can make me this much reduced offer. Which i accepted with great delight which is now my greatest regret. Her false deal never realized and am i still being billed for the old one! I phoned and then was told to phone back later as they were offline. couple of days later i phoned again and the person could not assist me and transferred my call and the lady wanted me to go through all the checks again after holding so long, when i asked her if she is serious she dropped the phone!! Vodacom cannot make such ''wonderful deals'' and still charge their clients. dont they think we check our statements! How can i get this resolved and get my money back for the over charges without having cheecky call centre people hanging up? Regards Lehane Matthysen