MTN *******, Not taking responsibility

On the 11.10.2017 i was contacted by mtn telling me that i'm due for an upgrade and i agreed to it, we did everything and i was told my new phone will be delivered in a few days, i asked the lady what was going to happen to the current contracted i mount i still owed on my current contract and she informed me that from the begining of November it will die out and i will start paying R679 the new contracted amount so i agrred i had no issues . On the 13.10.2017 i then got a message from mtn telling me that my number was approved for that upgrade. Shockingly on the 18.10.2017 i received my billed statement and it said the amount to be debited on the 20.10.17 would be R679.00 (Which would be the new upgrade amount i agreed to ofcoz).. So out of shock i called mtn yesterday assuming that there may have been a mistake as i was told i would start paying the new amount on the 20.11.17 not this month, the lady i spoke to said she didn't understand why i was billed immediately on the date i upgraded and she would help me log a complaint, we did that and she gave me a ref nr. So today 19.10.17 i received an sms from mtn saying my query was resolved but there were no details so i called mtn to get clarity on that. i spoke to another lady i asked her to check what it is exactly that was resolved and she said my complaint has been resolved and i will have to pay the amount due which is R679.00 instead of the R189.00 that i usually paid, so i told her that i'm still unhappy and she said it was beyond her. I then told her that i want to cancel the upgrade asap as i wasn't satisfied with her answer, i even told her that I have not even received the phone but i'm already getting such hassles, and she just said sorry she will find me a number so i can track the delivery status of the phone. But informed her that i didn't need the phone anymore, she then gave me a number to call she said it's mtn direct ********** 667, I called the number and i've been listening to music play for 19 minutes with no one answering eventually i hung up.