Can't connect to wifi

I have a new router model AC1750. I cannot get it to connect to Wi-Fi on my phone or laptop. I've worked with my Internet company, and proved that the modem is fine. I just don't know what to do with the router. I reset it, restarted it, but it just keeps re-asking for my password over and over again. Is there a phone number I can call? This is very frustrating to me and my limited knowledge of technology.