Your suggestion did not work 😒 It says number not registered for imessage
Sounds like you were give a number that previously belonged to someone who registered it to their Apple ID and never de-registered it...
Try de-registering it here: Deregister and Turn Off iMessage - Apple Support
Then re register it to your account.
The phone number you use must have SMS enabled from your cellular provider. That is how it will be recognized by Apple and be added to your Apple ID as a trusted device.
...With two step authentication of password and security question all is fine, Also two factor authentication work with the my new SIM...
You can only have one or the other security method for your Apple ID and would be listed at Manage your Apple ID. These authentication methods have nothing to do with your SIM card. Which one exactly do you have:
- Two-step verification
- Two-factor authentication
- Can you successfully log into Manage your Apple ID with your Apple ID that is being used with your iPhone?
- Is your iPhone listed as one of your trusted devices?
- Is your Apple ID secured with two-step verification OR two-factor authentication?
- Did you buy your iPhone directly from Apple new?
Answer to question-:
1) and (3) Yes, with my password I can log in well. With two step authentication of password and security question all is fine, Also two factor authentication work with the my new SIM
2) No
4) Yes, it is a genuine phone. Was working well with my old SIM / number, which I have removed from all my account
I have two step verification. I did not activate two factor authentication. Again my question is how to add my number to Iphone. Currently it says number unknown.
WHAT says number unknown? You have not yet adequately described what your problem is. Where are you seeing "number unknown?"
Does this have something to do with iMessage? Who is your carrier and what country are you in? If you are using an unsupported carrier, iMessage may not be able to activate with your phone number.
My new number but apple id already in use by another account