iPhone Battery & Power Repair - https://support.apple.com/iphone/repair/battery-power - battery replacement, cost, and time to repair. Including information about reduced rate for eligible iPhones.
iPhone Service Answer Center - https://support.apple.com/iphone/repair/service - "Learn more about iPhone service options, warranty, and pricing." Repair times.
How to find your nearest Apple Authorized Service Provider (AASP) or Apple Authorized Distributor (AAD) - https://locate.apple.com/country
iPhone Battery & Power Repair - https://support.apple.com/iphone/repair/battery-power - battery replacement, cost, and time to repair. Including information about reduced rate for eligible iPhones.
iPhone Service Answer Center - https://support.apple.com/iphone/repair/service - "Learn more about iPhone service options, warranty, and pricing." Repair times.
How to find your nearest Apple Authorized Service Provider (AASP) or Apple Authorized Distributor (AAD) - https://locate.apple.com/country
It seems to vary depending on the country. The $29 price is only for Apple Stores in the United States. The price is different in other countries if performed directly by Apple through an Apple Store or one of their service centers.
Since Apple doesn't have any Apple Stores in Bulgaria, I'm not sure if there's a set price for the service. You would need to contact an authorized service center in Bulgaria to ask what their price is. Apple doesn't set the service price of their service providers outside of the price Apple pays to them for warranty work.
I can't read Bulgarian, but here's the local page on batteries:
Appliese to Bulgaria? Can I change the battery in Bulagaria?
