Block Audio / Video chat

I have a remote location with WIFI that is accessible by many users. Problem is that the the backbone is a Satellite ISP has high latency and very limited bandwidth. Due to budget limitations I had to settle with a Asus N600 (RT N65-U) router.

In the QOS setting I gave email and web browsing the highest priority. And the lowest to video streaming and online gaming.

My concern are FaceTime, Google Talk, FaceTime video call, Skype Phone and Video chat etc

I want the text chat to go trough...

Block Audio / Video chat