In B2B, does difficult registration get you more users?

I'm working on a B2B startup and we are moving from a free open registration process to a closed registration process that requires a sales phone call to create an account on the website.

Has anyone else found that for B2B sales you paradoxically get more users if you have a closed registration process as opposed to an online user registration process?

So you get more registered users by making it harder for each user to register?