Pathetic service

In October 2018 I called in to upgrade and was offered a special rate of R699 for premium which would be valid till October 2019. Firstly when I go onto my profile on the self service it says the special is only valid until April 2019 and not October as initally advised when I agreed. Now I'm paying the agreed amount, however I keep getting messages to say I have an outstanding amount. I've called in 3 times in the last 2 weeks to explain my story and get reconnected. Every time they say they will escalate and the finance depart will call me to rectify. It seems like the finance department do not exist or cannot do the job employed to do. I need this rectified urgently as I keep calling in to the call centre at my own expense because of your employees not doing their job. My customer number is ********** 8.