client/User chat application

Let’s say I’m building Whatssapp application with Whatsapp’s servers as a link manager between user A and user B. Of course some Whatsapp’s servers or nodes should buy Blockstack’s tokens or coins in order to join Blockstack network and get the network service. But I do not want the users or clients to buy coins or tokens from Blockstack to join the Whatsap network because users/client aplications will object if they have to pay to join the Whatsapp network. How do I make users do not have to pay to the Whatsapp network I build on the Blockstack network ???