We bought an iphone Xs kini in japan , but when we got home in Philippines my cellular is not availble how can i fix it?

It could be the Japanese model does not support Philippines cellilar networks.

Find the iPhone that’s right for your country or region. - iPhone - Supported 5G and LTE networks - Apple or iPad --> iPad - Networks - Apple

It could also be you purchased a phone linked to a specific cellular carrier. Click on the link to read Apple's support article on how to unlock your iPhone for use with a different carrier. - How to unlock your iPhone for use with a different carrier - Apple Support - Only some carriers offer the ability to unlock iPhone for use on any carrier. Follow the instructions in this article to unlock your iPhone.

cathlene ~ With an old model such as an iPhone XS, it's worth checking that the battery is healthy enough to provide sufficient power to the iPhone's antenna for connecting with cell tower signals – so what's the Maximum Capacity % here?...

Settings > Battery > Battery Health & Charging

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That model was discontinued 4 years ago. In order to have it serviced, you would have to take it back to Japan. Probably more cost effective to just buy a new phone in your own country.