Can't send text message with O2 - error 0

[Tomh04]

Hello to everyone, 

I would really appreciate your help please, regarding a problem I'm facing currently with my Samsung S23, while trying to text a specific person/UK number (iPhone). Upon Send, I get a failure and this message pops-up "Can't send message with O2 - error 0". 

 - I do receive from that particular person, text and calls. I can call back, but I cannot send any texts there.

 - I can receive and send other texts to various other people/numbers from my contacts.
In the meantime, 

 - I've tried refreshing my Network Settings (go manual, disconnect / connect) and do a Reset Network Settings. 

 - I've checked my Mobile Messaging Center (+44...)
 - I've switched between different Messaging Apps in my device (Google and Samsung)
 - We've both checked our Messaging and Calls Block List, just to be sure.

 - I've Restart and Shut Down my device, plenty of times.

None of the above helped. 
Additionally, from my device and using a different SIM (dual sim / not UK , different provider here), I was able to text that person without any problem!
I currently hold a Pay-Monthly plan with O2 and I was moved here just recently, from Virgin.

Any idea what could be the problem or something else which I could potentially check? 
Thank you in advance

[Tomh04 · Accepted solution]

Hi @ZJokerZ,

Actually I've found out just a few days ago that this issue has been somehow sorted.

I am now able to text particular person/number, without any problem and my message goes through.
Both of us, did not change anything at out devices.

I am not fully aware if O2 made any change; however, I never really reported officially this issue.

It could be though that the problem was coming from the other provider.

In any case, I believe I should now close this issue.

Thank you all for your valuable help and support here.