You can definitely use windows phone in the Philippines, I know some Filipino who uses WP, also I went there with my 1020(unlocked) and haven't found any major problems yet, but there are some issues I dealt with like GPS having problem picking up signal leading to unusable maps, maybe its the fact that some roads in the Philippines aren't established yet or still unknown(its pretty common, most road in the regional areas doesn't have names)
To the OP, please login to your mobile nations account and tell us what problems you/WP are dealing with
so we can help you