Can we catch a taxi outside the train stations in Bonn and Munich? Will not have a phone to book.
Of course, taxi tend to be where taxis are needed.
OP said “We will not have a phone.”
You do not need a phone when you are at train stations and airports! The taxis are lined up waiting for you.
Munich: exit the train station on the north side (coming from your train to the left); there are usually numerous taxis waiting.