Can I replace my iPhone battery at 89%?

No, the battery would have to be down to less than 80% in less than 12 months. You still have approximately a year before you will need to replace the battery. Current cost is $89 (U.S.)

Eleven months old is not "basically new". Also, comparing an iPhone 14 Pro to an older phone is comparing Apples to oranges. Newer phones are more powerful in a number of ways and will therefore deplete a battery more quickly.

But, as Bob Timmons said, you've probably got at least a year before you'll need to replace the battery. Stop checking battery health and just enjoy using your phone.