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As a process of elimination can you try the Sim Card in another phone and another sim card in your phone which is advise I always try to give in all my responses in connection to such issues.
This can rule out the phone.
This can rule out a sim card going faulty which can be replaced by Vodafone via a blank sim card and sim swap.
Also is this happening everywhere you go ?
i.e it could be your masts status-checker.
Is this happening to all texts to all your contacts ?
Please also check any possible blocking options in your phone and ask the recipients to check with their network and phone blocking options.
It may also be worth carrying out a forum search for other possible avenues.
🌈Stay Safe 🌈
Current Phone > Samsung Note 10+ 5G _256Gb > Model: SM-N976B.
Samsung One Ui 2.1 / Android 10.
Samsung Gear s3 Frontier Watch.
Samsung Galaxy Buds.
I notice you had a problem with text messaging previously here https://forum.vodafone.co.uk/t5/Android/Can-t-send-text-messages/td-p/2603552
I am wondering if this a recurrence of the same problem or SIM connected especially when you have signal. Take a look at some of the self help tips in this link Network Issues . As you can see Vodafone's advise is to try your SIM in alternative phone, this will rule out a SIM card issue.
Also make sure you have the message centre number as +447785016005.
You can also try updating your SIM on the network by going into your connection settings, select an other alternative network, wait for it to reject the request and back onto Vodafone.
Further help from device guides here: Device Guides