2yrs contract being converted to 3yrs

I took a data contract for 3GB with Telkom mobile in Oct 2013 and after a year i decided to upgrade it to 5GB because i needed to use more data. So last year in Oct the contract was suppose to mature and i went to their shop and i was then told that in 2014 when i upgraded my contract, it was restarted from the beginning which means now it expires in Oct 2016. I did not cancel an existing contract and then start a new one, i only upgraded an existing one to a higher package. In Dec last year a lady called from Telkom to inform me that the info I got from the shop was incorrect and my contract has expired already. She then said i can go to any shop to upgrade and i will be refunded the monies i was charged after the contract expired. I then went to the shop and only to find out that it did not expire and it only expires in Oct 2016. So this means this contract will run for three years instead of two. So i do not understand why the lady who called said it expired and also the fact that i was upgrading an existing contract but someone cancelled the contract and started a new one. The WI-FI device i got with the contract is very old and hardly works anymore...This is unacceptable!!!