@Dsibbald
you can try reseat the SIM card and Make sure your phone is off before removing your SIM card,
1. power off your device
2. take out the SIM card,
3. waiting a 1 minute,
4. put it back and power on,
5. toggling airplane mode off/on,
and you can try to reset network settings and Changing APN Settings,
for iphone
Go to Settings > General > Reset > Reset Network Settings.
This also resets Wi-Fi networks and passwords,
or visit Here link,
APN Settings On An IPhone click Here link,
Ensure you have the correct APN settings by visit Here link,
Select the brand and model of your phone, After doing so, you will be provided with the exact APNs required for your phone on our network.
and try manually selecting network "3G ONLY"
for iPhone visit Here link
or Here link
for iphone go to Settings > Messages > To turn iMessage on or off,
Turn your data on to send a Picture Messaging in world-wide,
if your data is off and your home internet Wi-Fi is on is not going through the Picture or a video messaging,
you have to do this to going through you will need to turn your data on to send a Picture or a video messaging in world-wide,
and do Rebooting your phone ,This is quick and simple,to refreshing your network,
*what is meant by rebooting the device turn off and turn it back on.
on an iPhone, go to Settings > Messages and turn on MMS Messaging. If you don't see an option to turn on MMS Messaging or Group Messaging on your iPhone,
try to check update your device,
review
My texts to a group message are failing a… - Apple.
Failure sending group SMS - Apple.
If you can't send or receive messages on your iPhone,Apple Support (CA)
