How to change RDS licensing mode from ‘per user/device’ to ‘Remote control for administrators’ on Windows 2008 R2 server

We have installed windows 2008 R2 enterprise on a Dell server. This server is placed remotely in data center and only administrator is going to access it for maintenance purpose. No multiple users or client remote access is needed

Now during 'remote desktop services' role installation network admin accidentally selected 'per user/device' licensing mode. Because of which now 120 days free try period is ticking. Since only administrator is going to access this server remotely we need to have 'Remote control for administrators' licensing mode (like windows 2003) on it.

How we can change licensing mode from 'per user/device' to 'Remote control for administrators' on 2008 server?

Also will it be possible to do this change remotely using RDC session itself? or do i need to change it using physical console (if remote access is gonna be disabled during switch)?