Since nawala yung phone mo, need mo lang gawin is report agad sa Globe so they can temporary disconnect your line until you get your replacement sim. As for the contract naman, need mo lang ituloy with the same monthly fee walang idadagdag unless papaputol mo na yung line mo which is subject to termination fee (remaining months of your contract + Php 500 for the admin fee).
Your subscription fee would remain the same for the duration of your contract (even if your phone is lost or stolen).
There are no charges when you request for a temporary disconnection and you can do it via hotline (211 on mobile or 02.730100 on landline).
Losing the phone doesn't mean the end of your commitment po. You can visit the nearest GBC to get a new SIM or temporarily suspend the service (which you can also do by calling the hotline or doing it via MyAccount).