EdgeRoute Lite Data Cap over Cloud Radius

I have a client with a VSAT internet connection that we are providing to them and they have an edgemax router lite. We would like to Cap their usage through PPPOE.

The router is currently setup as follows;

eth0 = VSAT (WAN Internet)
eth1 = LAN -

The client has a 125GB monthly cap on their usage and we have setup the tariff on SPLYNX which is a hosted cloud server.

We would like to have this router connect to our SPLYNX cloud radius on and i asume this could be achived through PPPOE “Correct me if i am wrong” can you please kindly assist with this setup