MTN let's me down big time!!!

MTN at WonderPark shopping centre in Pretoria sold me a data card for my phone and I loaded a R250 data card that gave me a 100gigs for the month of June. The gigs shows on the app, but doesn't work. After several attempts to call the Helpline, a consultant said that the card is most probably locked to work on a router only. We I went back to WonderPark, the card was tested in several devices in the store, but did not work. The consultants then threw up their hands and told me that they don't know what is going on and can't assist me any further. I can't get a refund, nor can the gigs be transferred to the next month while I must try and get it sorted.( As I said....they couldn't). Goodness knows what I can do as I don't work for them , or have the knowledge? Then I was ushered out while telling me I have lost my money spent a their Store. Sorrrrryyyy