Just not happy ..... Router and Signal MTN

I have never been so exhausted and dissapointed in a product that I recently got from MTN... We have received a ZTE home router on the 1st of August 2020 and ever aince then we are unable to use the wifi properly... We have taken it back to the MTN store where we got it from to cancle the contract before the 7th due to us being unhappy but they wouldn't even take it back... We got told to phone 135 to get the sim card activated which we have done... We also went back to MTN 6 times due to the router not working... Tell me why do a person get wifi???? Obviously to enjoy the internet and to watch movies... But guess what we have not yet been able to watch one full move due to the router/signal disconeccting every 2sec.... We have had enough !!!!! Please could you get intouch with me so that this can be sorted out or I will take this futher..... I am NOT going to pay for a service I dont get!!!!!!!