When I'm not around wifi and try to get online, phone won't use cellular unless I manually turn off WiFi. Can I set up the phone to use cellular automatically whenever wifi isn't available?
I had a similar issue and first found that the phone had Mobile Data turned off. Then under the Wi-Fi settings, I had to turn off the option to always scan for WI-FI or it just wouldn't want to use the network. Not sure if that will solve your problems but worth a check.