MTN makes it impossible to upgrade

I have been trying to upgrade my phone contract for months. At first, MTN kept moving the date on which I could upgrade. When it was finally authorised, I tried to upgrade online and by phone several times, with no success as the transaction always gave an error at the last moment. Finally, I was given a number for a certain Nombulelo Luhabe, who would supposedly assist me on WhatsApp. This individual was quite unresponsive, but after half a day and a number of messages, she informed me that the upgrade was done and that she would phone me the following morning to conclude the matter. Needless to say, the phone call never took place, and the upgrade has still not been completed. Meanwhile, my contract was changed to a more expensive option without my consent, following a snooty message from MTN to inform me that they were changing the plan since the contract had expired without being upgraded.