iPhone 13pro calls going straight to voice mail

My 3 teens just got iPhone 13 pro two are activate the other is not yet. The two activated are having issues when we can their numbers it guess straight to voice mail their phones do not ring, but you can face time them and phone rings call goes through. And one of them isn’t receiving text confirmation codes green third parties exactly verification codes from cash app or software confirmation codes sent green a website to verify his accounts with codes sent to text, yet he can receive our text.