No assistance with upgrade

I've been with mtn for years now and I'm really disappointed that no one was able to assist me even though I have proof of the adverti*****t. On Thursday the 19th November 2020 I saw an advert on the mtnza page for the Samsung note 20 which I was interested in upgrading to as I've been waiting for a good special to do an upgrade. I've contacted the mtn upgrades as well customer care and no one was able to assist me with my upgrade. I'm not sure if it was falsely advertised or not but I feel that they should honor the price especially since I've got proof that I've seen the advert of the contract on the Instagram page.. I would appreciate it if someone in management could assist me with my upgrade..