MTN is useless

We bought a router (Fixed home lte) about 3 weeks ago. The network works for like an hour and it disconnects, I will need to restart the device every time it does that. I called mtn call center more than 10times on a daily basis without assistance, I'm told the address is wrong, when I go back to the shop they say the address is okay. Who to believe n who not to believe.. This is sickening as I have students attending online class using that router.