I do not have a data plan I use WIFI from my internet provider but when away from home I find I can send messages but when there is a response to a message or someone sends me a message I only receive it when back to my WIFI environment.
iPhone 11, iOS 16
Hi there Rickmucker,
Thanks for posting to Apple Support Communities. We're happy to help.
Without a cellular plan, you'll be unable to send a message to a telephone number via SMS. You can send and receive messages only via iMessage to other iMessage users when connected to Wi-Fi. If you're able to send messages when out and about, your iPhone must be connected to Wi-Fi or a personal hotspot.
See here: Use Messages on your iPhone or iPad
That should help. Let us know if you have any questions.
Take care
I can send messages when data and wifi are off but cannot receive messages
