I live in a small town far away from any service so DSTV LTE was a good option I tried MTN but they were very unhelpful.
The unfortunate irony is that DStv use MTN for their internet in this new venture.
My best suggestion is if you can log into the settings of your router, the router stats should show which "Cell ID" you're (supposed to be) connecting to, unless your connection is so dead that you can't even get to the login page via, for eg. using :
192.168.1.1 (in search bar of a browser).
If you can get the Cell ID, and other related info, jot it down then call them again & tell them you need them to get MTN to check that tower you're connecting to.
MTN also have a 3 page online fault /congestion form you can fill out & send to them directly to look into, but don't hold your breath for a quick, or in fact, any answer .... though you'll get a reference number after filling it out you can then give to DStv, for subsequent, possible feedback.
www.mtn.co.za
MTN seem to be having issues recently - mine, and others speeds have been down recently, either directly through MTN or via Cell C / Supersonic.
The recent power outages must have played a part in all this.
Try DStv Internet via WhatsApp, if you haven't already ; might be more helpful / clued up.
Good luck with it.