Apple iPad 2
Apple iPad - Turn Wi-Fi Assist On / Off
Apple® iPad® - Turn Wi-Fi Assist On / Off
When turned on, Wi-Fi Assist can result in unexpected data charges.
From the Home screen, navigate:
Wi-Fi Assist switch
to turn on
Wi-Fi Assist is turned on by default.
Wi-Fi Assist enables the device to automatically switch to cellular data when Wi-Fi coverage is poor and switch back to Wi-Fi when the Wi-Fi signal improves.
Wi-Fi Assist is compatible with any iOS device on iOS 9 or later, except for these models: iPad 2 Wi-Fi+Cellular, iPad (3rd generation) Wi-Fi+Cellular, and iPad mini (1st generation) Wi-Fi+Cellular.
For more info on Wi-Fi assist, check out this