Concrete formers. Or landscapers who do retaining walls.

Your question does not give us much information about the situation, but adding a door to a basement can be risky. Is the section of wall you are removing a structural component that supports the building above? Will there be basement flooding issues? I'd talk to a structural engineer.

This post was edited by edlincoln on Wed, Feb 5, 14 at 13:16

Good points!

You must be a specified distance from a corner, you have to provide a drain and for the continuity of the footing drains. In a cold climate, you may need to insulate the foundation on either side of the opening and excavate and add to the foundation wall below the opening. Installing a steel header above the opening, assuming a single door, doesn't require an engineer's input. Depending on the retaining wall system used, you may have to excavate five feet or more back from the eventual opening.

See the linked article for the steps involved. This is not a diy job.

Here is a link that might be useful: Adding a Walkout Basement

This post was edited by worthy on Wed, Feb 5, 14 at 8:33