IMessage only recognize Apple ID / Email but not phone number. Why?

Question

I have a small problem with the iMessage. My phone only recognize and auto detect the apple ID but not the phone number who are available for iMessage. Does anyone experienced the same problem?
These print screen below is 2 examples from my contact who actually available for the iMessage with their phone number.

Answer 1

i think i have found a fix for this its worked for me so its worth a try. You will need the other persons phone to do this.
1) Delete the contact from your phone.
2) On your phone go to Settings > Messages then tap receive at, it it has your Apple ID e-mail address at the top tap that and sign out this will remove your e-mail address from iMessage leaving just your phone number.
3) Go back to Message settings turn off iMessage.
4) Turn off your phone and back on.
5) Go back to Settings > Messages and turn back on iMessage it will then reactivate iMessage
Now for your friends phone
1) Go to yourself on your friends contact list and remove your e-mail address if they have it saved.
2) Go to Settings > Messages then tap receive at, if it has their Apple ID e-mail address at the top tap that and sign out removing their e-mail address.
3) Go back to Message settings turn off iMessage.
4) Turn off their phone and turn it back on
5) Go back to Settings > Messages and turn back on iMessage
once reactivated on both phones follow these steps.
1) Send a message from your friends phone to yours
2) On your phone the message should come through and will have your friends mobile number at the top
3) Reply to your friends message.
4) Save your friends phone number as a contact again leaving the the country code (i.e UK country code +44)
5) Delete the message between you and your friend on your phone then compose a new message and and select your friends number and it should automatically send as a iMessage send the message then go back to your contacts remove the Country code from the number and from there on then the iMessage will detect that persons phone number as a iMessage compatible device.
This has worked for me and 3 other of my friends who where having the same problem with a number of their contacts, it seems the error is more to do with your friends phone, when activating iMessage for the first time it automatically defaults to the Apple ID and in some cases causing the phone number not to register correctly with the Apple servers this step by step removes the e-mail and reactivates nothing but the phone number with the iMessage servers.
Hope This Helps.