Samsung chat messages received on old phone

[Karen222]

Earlier this week I switched from a Samsung Galaxy S8 with Vodafone to a Galaxy A71 with O2.
The Samsung Messages app on the S8 is enabled with chat messaging, but the same app on the A71 is not (O2 have not yet enabled the feature for that model) so I can only send and receive messages as SMS/MMS.
Hopefully O2 will roll out this feature soon but I can live without it for now.

The problem I have is that ever since my old number was ported across to the A71 on O2, whenever anyone sends me a chat message it is still being received on my old S8 even though the sim is no longer active.

Can anyone explain why this has happened? I need to

[Karen222]

Lol posted too soon...
Is there something I need to switch off? Or just remove inactive sim from old phone?

[MI5]

@Karen222 

You phone number is still registered in the message app.

You'll need to delete it from your S8.

[Karen222]

Thanks. I'm clueless on how to do that

[MI5]

@Karen222 

Open message app.

Tap the 3 dots menu.

Go to settings >Number and remove your number.

[Karen222]

Afraid there's no option within Samsung Messages to do that.
I've been advised by Samsung support that I need to contact Vodafone to remove number from their network
Thanks for taking the time to help!