Sometimes smartphones will keep using cellular data even when connected to WiFi. Your smartphone’s software does this in an attempt to boost data speeds, but if the cell network is weak this can result in slower performance than just using WiFi as your phone jumps back and forth between WiFi and Cellular. If your cell data is metered it can result in overage charges.
If you are on a WiFi network and the performance seems slow or inconsistent you can disable this feature in the phone’s settings; for iPhones it is called WiFi Assist and in Android it is has a few different names depending upon the manufacturer, such as Adaptive WiFi or Adaptive Connectivity, and is found in the mobile settings. You can also disable mobile data, just don’t forget to turn it back on when you are done.
