Since there is no "herra" or "rouva" used I don't see how "Hello Mr Pöllölä" could be a possible translation, even if it feels more natural to include the title.
Regarding last names, people don't really use them with anyone unless the last name is someones nickname of sorts or the people talking are in the army. Pupils/students use their teachers first name when talking with them, for instance (or just say "opettaja"/"ope" - teacher).
Not using Mrs or Mr is often considered rather frank, and sometimes rude / flippant. It is not usual for such greetings