Turning off cellular data will not impact your ability to send or receive text messages.
Instead, your iMessages will be sent as SMS (text) messages.
However, even if you turn off cellular data, you can still use wifi to send iMessages and use apps like WhatsApp, etc.
Do I need mobile data to send texts?
Normal text messages (just text) do not use data so mobile data isn’t needed.
When cellular data is off can you text?
It’s absolutely OK to turn off Cellular Data if you have a minuscule data plan or you don’t need internet when you’re not at home. When Cellular Data is off and you’re not connected to Wi-Fi, you can only use your iPhone to make phone calls and send text messages (but not iMessages, which use data).
Can you text without WiFi?
It is not possible to use the app without one or the other, unfortunately. WiFi and cellular data plans are what connect your device to the internet and Textfree uses the internet to allow you to text for free.