I recently bought 2 new handsets on contract with BT. My daughter uses one. We both ported our numbers across and the phones work fine but to others it looks like we’re calling from the original BT number rather than the ported number (even though incoming calls /messages to our ported numbers are fine) and when we message each other we get each message twice and as a text not I message. Any ideas?
In regards to the iMessage, have you check that iMessage is enabled in the message settings? If not you will need to switch it on, and sign in. Once signed in ensure that you select send and recieve from - as your current number (the number you are keeping)
You may find that onces your porting is complete that you need to let iCloud and Apple know that the device has swapped mobile numbers and that old orginal number you are porting in is linked to that device and not the BT One. Its a simple process.. Speak to the mobile team and check the status and then we can help with imessage if needed.