Can i change my battery

Yes, just ship your phone to an Apple Store or bring it in person.

If your phone is under warrant or have AppleCare+, it will be free to replace.

If your phone is out-of-warrant or don't have AppleCare+, it will be $69 to replace.

Considering your battery health is still in the 80-100 range, just wait once the battery health reaches 79 or under then it will be a great time to replace your phone's battery.

Start here, iPhone Battery Replacement - Official Apple Support

nerieza wrote:

My battery is 89 %

Apple considers the battery fit for use until it drops below 80%. Unless they can diagnose some other problem, they won't replace it at this stage.