Thanks for contacting TextNow Support!
You are correct that the phone should default to wifi whenever possible, but it's important to note that the phone needs to have access to a wifi connection to use it. in other words, if you're using a connection that needs a password to access, you'll need to enter the password for the wifi connection before your phone can use it. Also, if the wifi connection is a public one (for example at a cafe or library), you'll often need to open a browser window on your phone to finish signing into the wifi network.
A quick way to test whether your phone is connected to wifi or not is to turn off Mobile Data in your main Settings menu. If Mobile Data is off, your phone can only use wifi. If you're having trouble connecting to the internet when Mobile Data is off, you might have a problem with your wifi connection, or need to sign into your wireless network.
And finally, even if you go over your 100MB limit, we don't turn off your service or charge overages. All that happens is your connection switches to a 2G connection, and you'll still be able to call and text without the need for wifi.
If you would like more help with this or any other aspect of your device, please contact us at TextNow Support - 1-888-250-5255, Mon-Fri 9am-10pm, Sat-Sun 9am-5pm EST - or use the chat window below to speak to one of our chat agents.