incorrect line upgrade

I received a call from Steven on 08/01/2015 advising that I am due for an upgrade, we spoke both lines were upgraded & I received my new phones the following week. I decided I am no longer interested in a laptop therefore I called Steven to cancel & he said it was fine the deal didn't go through. I then went to the Vodacom outlet to upgrade & to my surprise I was told I cannot do that because my contract has already been extended until 2018. I spoke to Steven on numerous occasions & he advised that this will be reversed until today this was not done. I decided to then go & upgrade on a different number & the lady who was assisting me advised me that there is negative reports on the bureau so ? do not qualify. I want to know how did head office manage to upgrade one of my lines if I have a negative credit record? If they were able to upgrade one line , why can't they do the same with my other line.