I still have the issue in beta 9. Understand that I did not have this issue at all on IOS 11, the only thing that has changed on my account was installing IOS 12 on my device only. We all have our own phone number and this should work. It is a bug. we should not have to change our accounts in order to correct and Apple problem. I have had 6 Iphones on the same Apple ID for 5+ years with out an issue. All 5 of the other Iphones on my ID do not have this issue and they are on IOS 11.