Devices connected without internet or dropping connection

Hi we had Virgin broadband installed last week and all has been fine but this morning the connection has been dropping on and off on all WiFi connected devices all day. At some points some devices have worked when others have not. My phone a Samsung Galaxy S20fe has been the worst affected of all and after speaking to an advisor on the telephone for over an hour some devices hooked back on but I am still unable to woth my mobile phone. After only a week this is not the best start to being with Virgin and I am using up all my mobile data and unable to complete worn at home without a stable Internet connection. Please help!