Unable to enable MMS messaging on iPhone
cant Turn on mms messaging on my iPhone because it is missing in my settings
[Re-Titled by Moderator]
Original Title: MMS messaging
Re: "MMS messaging: cant Turn on mms messaging on my iPhone because it is missing in my settings"
You may want to turn on cellular data for the Messages app on your iPhone:
(Note: provider charges may (or may not) apply, depending upon provider / plan etc.).
See: View or change cellular data settings on iPhone - Apple Support
Eg: says:
"Set cellular data usage for apps and services
Go to Settings 
>
Cellular, then turn Cellular Data on or off for any app (such as Maps) or service (such as Wi-Fi Assist) that can use cellular data. If a setting is off, iPhone uses only Wi-Fi for that service.
Note: Wi-Fi Assist is on by default. If Wi-Fi connectivity is poor, Wi-Fi Assist automatically switches to cellular data to boost the signal. Because you stay connected to the internet over cellular when you have a poor Wi-Fi connection, you might use more cellular data, which may incur additional charges depending on your data plan. See the Apple Support article About Wi-Fi Assist."