Happy but upset loyal customer!

Over all I love Vodacom, fast internet, great signal and friendly customer care staff but my last experience was a bit saddening.

I received an sms, saying that i can upgrade, very excited i tried to upgrade online but unfortunately there was a mix up because my contract used to be on my grandfathers name. But this issue was sorted out shortly after speaking to a friendly consultant who went through a lot of effort to help me. With the dates fixed i went to my local vodacom at lephalale mall to upgrade, because my sms said i can. The man who helped me at the shop was friendly and i received my phone immediately. The first payment went off, all was well.... until i received my latest sms statement, it upset me to see that i need to pay R1258.14. When i phoned to enquire about it i was told it was to pay for my old handset, which seems fair except for the fact that of I knew this i wouldnt have upgraded immediately. There is no mention of this in my paperwork and this has never happened with my previous upgrades.