white_tiger It should be free. You can request it online via accounts.globe.com.ph (User guide found here: Deactivate International Roaming | User Manual | Help and Support). If you prefer text or calling:
You can text GROAM OFF and send it to 2884. You will receive a message to confirm your request for deactivation. You can also call our roaming hotline at +6327301212.
Just remember that it's recommended that you deactivate your GROAM service within 24 hours upon arrival in the Philippines.