Money making scheme

Worst provider- they installed wifi at my parents house and never checked coverage before installation. My parents struggled with connection in their room and phoned them and the manager advised that the technician should have checked coverage and explained all options before installation. After they confirmed that the technician did not do as he was supposed to, they still wanted to charge a call-out fee. Now we wanted to help my parents with a battery backup for loadshedding and the connection is completely gone. Now they again want to charge call out fee but if they have access to the router why can’t they check what the issue is. You also don’t have access to your router. Just trying to make money around every corner because we can’t even connect a booster or backup battery, you have to install it thru them obviously.