Switch to whatever network is faster with Wi-Fi Assist
When Wi-Fi is available, it is always a better option to connect your phone to that network. The first reason is your data plan may be limited to a certain amount of gigabytes of browsing, and it is better to save them for when you have an urgent need. The second reason is that cell signals can be flaky.
If you often go to places where there is little to no mobile signal, then it would be a good idea to turn Wi-Fi assist on. This feature can be accessed by going into the “Mobile Data” section on the “Settings” app. Once turned on, it will tell the phone to switch from wireless to mobile data according to what works faster.