Vodacom early upgrades- a huge con!

I really hope that posting on this platform will help to resolve my issue. I have a contract with vodacom and have been a customer for close to 20years. Around mid-June I received a text from a vodacom service provider saying that I qualify for an upgrade. I called the upgrades department and was subsequently upgraded. The lady who upgraded me then told me I would receive an sms confirming the upgrade. She also told me that I should NOT worry if the monthly amount on the sms is not what we discussed (contract amount). And so I did receive an sms with a higher than expected amount. I ignored this as I was informed to do so. When the bill comes- I find it is even higher than the incorrect sms amount. I called the call centre and was informed that I was paying for 2 handsets because my contract had not yet expired. First of all I was prompted to upgrade, secondly When I upgraded I was NOT informed of this and thirdly the upgrades department blatantly **** about the “incorrect” amount that would reflect on the sms. Had she not told me that I would immediately have called to query the amount!!! Surely this is total *****? Their calls are recorded so can they not trace this? I have now called them 3 times and at the end they say I am still liable for the headsets!!! How is this possible when THEY **** about the amount???