Bad customer service

An agent from MONDO called me to persuade me to subscribe to MTN LTE ROUTER. They did the coverage assessment on my address, and told me that there was. They delivered the router,but it didn't work. After numerous calls and to and fro to MTN, they told me that there was no coverage in my area, and i had to return the router which i did immediately. They're now giving me a run around for my refund from April 2022 until to date.