What is the best approach for the following scenario:

1) A publicly available app (available in app stores) which is used by end users to make use of services offered by multiple companies.

2) These companies maintain their services also using a mobile app.

I'm not sure on how to solve the second part. Having one app for both enduser and admin functionality, secured by username/password doesn't sound like a good idea. This would leave the only option of developing a separate admin application for the companies.

What is the best approach to deploy "admin" like mobile apps to companies only, for Android, iOS and Windows Phone?

Some additional information:

Public App ----> Servers -----> Multiple Company Apps

The public app shows all companies offering their services. An end user uses the public app to order something from a specific company. The order is sent to our servers. Our servers send the order to the associated company. This order is displayed on the company's admin app and given the option to accept the order.