Can you give an example of where you heard this?
As far as I'm aware, there is no three-word phrasal verb 'get up with'. If you say 'I got up with Sam', you are simply using the normal phrasal verb 'get up' followed by the preposition 'with'. You'd say this, for example, if you and Sam were sitting in a waiting room, Sam got up and you got up ( i.e. stood up) at the same time.