Transfer to new (to me) phone has duplicated

You need to register your new phone to the phone number and deregister the old as below.

In Europe there is no need to involve the network carrier

Assuming you have moved the SIM card or eSIM to the iphone 16pro...

On the iphone x do all 3 steps here, don't miss any out

1.   Settings, Apps, Messages, turn off iMessage  

2.   Settings, Apps, Facetime, Turn off Facetime,  

3.   Power down the phone

On the iphone 16 do all 6 steps here, don't miss any out

1.   Settings, Apps, Messages, turn off iMessage  

2.   Settings, Apps, Facetime, Turn off Facetime,  

3.   Power down the phone

4.   Turn on the phone again  

5.   Settings, Apps, Messages, turn on iMessage,  

6.   Settings, Apps, Facetime, turn on Facetime

Then ensure your correct number appears in the Send & Receive 

DurianEater wrote:

I had my iphone 17 stolen in Greece. I have recovered my accounts on an iphone x but now am attempting to switch to a 16pro running 26.5

The transfer didn't work so I updated the new phone from the cloud. Things seem to be working but nothing from the iPhone x has transferred. So now, SMS arrives at my old phone (x)and all the apps which are loading require logging into again. Seems I'm running two of everything. Is there a solution ?

Your 16 needs to be activated by your phone carrier in order to receive SMS.