This is possible but you wil pay a very high premium.

Kasi walang charges ang isang network if the call is from the same network (like Globe to Globe). Same operationg cost for the network kasi yun, meaning fixed ang charges sa operation ng pagmamaintain ng network and etc.

Pero if different network, the caller (the network) will pay the called party (network) for every airtime na ginamit mo yung ibang system nung ibang network.