[chat] What is "Back channelling" ?

["Minh Van Le" <mvanle@xxxxxxxxxxxxxx>]

In TGP Internet's Standard Terms and Conditions, clause 20 states:

20.	TPG does not under any circumstances allow back channelling. TPG
reserves the right to charge Customers for any incoming or outgoing traffic
if this is breached at 20 cents per MB.

I was unable to clarify the meaning of "back channelling" from a helpdesk
officer. Would somebody explain to me what "back channelling" means in the
context of their T&C ?