Welcome to Vodafone Community
I've had my P20 pro for maybe 6 months now and I've an ongoing issue when sending text messages.
Frequently, I'll get a warninw message saying a text message hasn't been sent. I will try and resend several times, getting the same message. I then frequently get replies to said unsent message, asking why I've sent it multiple times.
Any ideas why this occurs?
Does this happen when sending to a particular contact or is it happening no matter who you text ?
Can you recieve incoming texts Ok ?
If a particular person then the issue could also be at their end.
Have you recently ported your mobile number over to Vodafone from another network?
If so it could be a split port issue where not all the files have properly settled. Customer service on 191 can help.
Other avenues > This could be a mast congestion problem or a general mast issue @Ben_W
Does this happen everywhere you go or in one particular general area ?
You could as a process of elimination try your sim card in another phone to see if the issue persists.
And try another sim card in your phone.
Sometimes the sim card itself degrades and if so a Vodafone Highstreet Store can perform a sim swap to replace the card. Take some photo ID.
If it's the phone at issue and all the settings and preferences look to be right then a Vodafone Highstreet Store can send it away for a diagnostic or reach out to the manufacturer.
Some possible help links >
A Google Search may yield further advise .
I wish you all the best with this situation.
Current Phone > Samsung Note 9 _512Gb > Model: SM-N960 Hybrid-Duos.
Samsung One Ui / Pie.
Samsung Gear s3 Frontier Watch.