Vodacom incompatance

Yet again Vodacom happy to take a person money. I have a contract that was up-graded on the 7th of Dec 2013 and up-graded the contracts now on the 21st of Nov 2015 - so I get billed for both contracts this month, on calling Vodacom I get told that I took a 24 month contract so I have to pay both the charges till the end of Feb 2016. I have two issues here does Vodacom have longer 24 month periods than the rest of us as to me on the 7th of Dec 2015 I would have been paying my old contract for 24 months which was what I agree to do, and should it have been the case where I had to pay both till the end of Feb why was that information not given to a person when up-grading. I told them I did not want to pay more now I am paying double - seems to me that they are just money hungry or they would for sure give the client all the information in my books. Sad to see Vodacom has not changed as this is the second time I have had issued and put something on Hello Peter when it comes to them.