Problems with MTN Home 5G router

Please help. My MTN home router has not worked except very intermittently (perhaps 4hrs) over the past week. The blue lights come on and say either 4G or 5G but when I connect any device to it I get a message that says "Connected without internet". I even took it down to the MTN branch in Ilanga Mall in Nelspruit where it did exactly the same thing. The told me to take it back home and wait for the technician to solve a problem at the tower... but surely I was already connected to a different tower in the mall which is 20km away? This router is clearly faulty. It's not lack of signal either, my other MTN SIM in my phone works perfectly... But I'm consuming all my phone data and more trying to keep my home connected. I don't have budget to keep loading LTE data when I've paid for the Home Internet package already. Please help.