Worst Customer Experience - MTN Upgrades

I was due for an upgrade on 1 December. It is now 4 December and I am still struggling at MTN stores to upgrade. They say a credit limit has to be approved in order to upgrade. It has been more than 3 days and the 'supervisor' hasn't responded. The matter has been escalated by MTN Rosebank, but still no response. I asked for the matter to be escalated again, but yet still NO RESPONSE. I have done 3 upgrades with MTN and not one of them hasve been a pleasant experience. Seriously considering changing service providers and would advise others to do so as well.