Frist I came over this post in the tech communities Add company name
Then I read and added this and they showed up.
But I could not figure out why all contacts needed company name, so I posted this question.
Then someone start to push me to do some more testing. And here is my conclusion.
1. If you add a new contact you don't need company name or email, just name and phonenumber. The phonenumber does not need to be on E164 can be strait forward. Restart the teams client and it shows up under Calls - Contacts.
2. If you have an old contacts that does not show, just do a change on it and it will show up.
This has been tested on a clean Exchange online (no-hybrid).
This will be the last blog in some time due to that I am going on 4 weeks vacation next week. Have a great summer and #StaySafe