Horrible service we are receiving from VUMATEL

Yoh,so we installed vumatel fibre wifi,but the service that we are receiving is pathetic.

Installation was done successfully,however the connection only covers certain areas in the yard about 5 - 10 meters away from the router,from further than that,no connection at all.

We are trying to get them to sort it out,but we are having back and forth,from sales department,to the technical department.

To put a cherry on top,we are told that we will be invoiced again,should they send out a technician to come check,because from their end everything is working perfectly,

Please advise as to what are the procedures of canceling your services.

Thank you.