phone purchased from Bulgaria

Google search says:

Unfortunately, you cannot purchase AppleCare+ online for your iPhone from Apple's website if it was purchased in Bulgaria. AppleCare+ is currently not available for purchase in Bulgaria, even if you try to buy it online from another country's website.

Consider waiting until you travel to a country where AppleCare+ is available:If you plan to travel soon, you could potentially purchase AppleCare+ in that country for your iPhone. However, it's important to check the specific terms and conditions beforehand to ensure coverage validity in your region.

See Buy an AppleCare plan - Apple Support

it will on,y be valid in the country/region of iPhone purchase