Unable to text to +44 numbers

[Nicip1]

I have just moved to O2.  My son sent me a message today but I couldn't reply to it, my text just failed to deliver.

His text showed his number started +44. I managed to text back using std format 07 number, but this showed as a completely different conversation. 

Then tonight I have tried to message another contact.  I change the number to start 07 before it would go. I had a reply but it said the number was from +44 and again I couldn't reply.

Can anyone tell me what's happening and what I need to do?

[pgn]

Check that your Settings are set correctly for you, Pay Monthly have a different message center from PAYG phones, @Nicip1 - details in here (pay particularly attention to the +44 bit:

Guide: Text Message Tips (not sent or received) 

See if that helps - if not, reply with phone model and the app you use to manage SMS messages on the phone.

Good luck!

[Nicip1]

The message centre number is correct.  I'm using a Samsung Galaxy A12 using Messages for text.  I did ring O2 for help and was told I needed to copy all my contacts to my SIM, however on doing so I now how what I call duplicates, even though only a few are recognised as duplicates when I try to automatically clean them up.  I did delete a load manually too.  However it says that around 280 contacts aren't on the SIM as the SIM is now full!

[pgn]

Details here on moving contacts from old to new smartphone without using the SIM, and how to transfer contacts from SIM to phone - if it helps, @Nicip1!

https://www.helpforsmartphone.com/public/en/samsung/galaxy-a21/android-10/guides/20/Import-contacts-...

[Nicip1]

Sorry only just managed to get back the page, I keep going round in circles.  My contacts have been moved from my old phone to my new phone, no issue there.  But a month down the road and I am still having problems with text messages.  I can send a text, then get a reply, but it shows on a completely different message stream, and I cann;t reply to it.  It's driving me mental.  I've actually got 4 message streams going between myself and a friend, and have to constantly search to find what they've replied to.  Really not happy with this phone at all