I also have a different phone to use in Phils and buy a Smart sim card when I arrive.
I still have my regular UK phone on PAYG (Virgin Network) so I can receive any emergency calls, also so I can receive calls from the care home where my dad will be staying for respite. Never had any problems either receiving or making calls. However I did make sure it was completely unlocked and ready for use with any network. This depends where you get the phone sometimes.
Being pedantic, dual band and tri-band only really mean that the phone can operate in two or three of the four bands available globally.
Normal European tri-band phones support the 900, 1800, and 1900 frequency bands.
Therefore they provide complete coverage in Europe, Africa, and Asia, and work on at least one network in most countries in the Americas.
Normal European dual-band phones support the 900 & 1800 frequency bands which is just the same as the same as Philippines.
So both will function.
