Infuriating Service

I paid for my fiber installation on Friday 27 May technicians came Wednesday 01 June, put the router in, left it with the red light flashing and never said anything.Its a day later I haven't received any communication,when I whats app the sales agents all they say is that they logged a query I even complained on their website but no one is responding.I haven't received any wifi username or password I'm just sitting there with a router thats not working meanwhile I have paid for their service in full.