*****ulent and miselading behaviour and offer from MTN South Africa

On the 6th December, I recieved a call from MTN, offering me an upgrade. According to the agent, who was being supervised by her manager; for only R100 more per month, I would recieve close to double my minutes and 30Gigs of data. I continously questioned the veractiy of this offer, but was constantly reassured that this was a special offer, considering that I have been with MTN for more than 10 years. Now, instead of the increase per month being R100, it is actually close to R400 per month. This morning, 27th December, I spent more than 1 hour on the phone with MTN's call centre who have pushed me from pillar to post but have not assisted to resolve my issue. I hold MTN accountable for providing me with information at the time of the upgrade; which I now see as *****ulent and misleading. The call recordings will clearly prove that the agent committed and confirmed that the increase will only be R100 per month. This is so unprofessional and is unacceptable. How can I pay an amount that i never agreed to pay in the first place. Daylight ******* and nobody at the MTN call centre knows the department that can sort this put, althouhg it is wihtin 30 days of the call. I need a MTN manager to call me now!