which branch should I acquire my phone here at Batangas Philippines

Hey there ciferio,

Thanks for reaching out to the Apple Support Communities.

To get started, when referring to your battery health capacity decreasing, are you referring to the Maximum Capacity shown in Settings > Battery > Battery Health? If so, the Maximum Capacity decreasing is expected behavior over time, and there are a number of different factors that can affect your overall battery health. This can include factors such as the number of charge cycles and how it was cared for. 

Just to confirm, are you seeing any alerts or messages stating that your battery health is degraded and a battery replacement is needed in Settings > Battery > Battery Health? If you're not seeing this message, and your Maximum Capacity is still over 80% then a battery replacement may not be necessary.

"A normal battery is designed to retain up to 80% of its original capacity at 500 complete charge cycles when operating under normal conditions." You can find this information in the 'Related Article' that was shared on this thread: iPhone Battery and Performance - Apple Support

From here, if you'd like to look into some steps that can help with optimizing your batteries performance, check out this link here: Batteries - Maximizing Performance - Apple

If the issue persists after going through the steps above, or if you are seeing an alert that a battery replacement is needed, we'd recommend reaching out to Apple Support for help with looking to the best service options in your area. You can reach out to Apple directly at this link here: Apple Support

We hope that's able to help.

Take care!