"Annyeonghaseyo ___ imnida" and "Annyeonghaseyo jeoneun ___ imnida" both have different definitions.
"Annyeonghaseyo? Jeoneun Bob* - imnida" is the formal way of introducing yourself in Korean (to your parents, teachers, etc).
When you introduce yourself casually, you take out "jeoneun".
"Annyeonghaseyo? Bob - imnida."
*Bob (name) is used as an example.
