If your WiFi is good, the phone will be as fast as that, because most all phones will use WiFi over cellular network. If you are out of the WiFi zone, it will just use the cellular network. WiFi or not, call quality and placement speed as well as sending and receiving texts won't be as fast as 3g or 4g, because calls and sms take place over the network, not WiFi (depending on the phone and/or carrier)