Telkom False advertising on iMac

Ordered an Apple iMac from Telkom's site. It's advertised as 4K retina. The Mac arrived just before Christmas and it's only 1920x1080. In other words, HD 1080p. Not 4K as advertised.

I contacted customer services. They told me to call Mondo and Sell direct - the companies they source stuff from. Neither one of those companies have my details. One doesn't even sell macs.

What's going on here? Who is responsible and will Telkom honour their advert by sending the correct device?