Include "businesePhones" in basic profile
According to https://docs.microsoft.com/en-us/graph/permissions-reference#remarks-23, now with permission:"User.readBasic.All" , only bleow properties would be visible:
Which means "businessPhones" is not included.
So it means normal user (not admin) won't be able to view other users' business phones in Teams, even these "other users" are their colleagues !
You never want to reach your colleague by calling their business phone !? So what's the point to keep business phone invisible to most users in same organization?
Just suggest to include businessPhones in basic profile.