Bad service KCS

Very bad service. Wifi router that was supp**** do not cover my whole house. I called and complained. The brought another router, and then the technician installed the old router to work as wifi range extender. Now, most sundays after 17:00, there will be absolutely no internet. Then they blame the extender. Last time i unplugged the extender, but they still said its the extender. They also told me that my tablet has a high ping between the 2 routers, even though i do not even have the tablet anymore. They will promise for a senior technician to come and check, its been how long now, he never came. They are very fast to ask for payment, but they do not have a clue what customer service means. Now i will refuse to pay until my problem is resolved. Im sick and tired now.