My Ifone iPhone 6s Plus has an old battery and I always charge phone daily because it discharges very fast. How can I replace its battery?

iPhone Battery Replacement:

Current Apple Prices:

• No charge for in-warranty or AppleCare+ plan.

Out of Warranty Prices:

• iPhone X or newer: $69 U.S. Dollars.
• Older models: $49 U.S. Dollars.

➢ Check AppleCare Coverage.

Click ▶︎ iPhone Battery Replacement.

Here is how to get an iPhone Battery Replacement - Official Apple Support

An iPhone 6s won’t be supported past iOS 15, with iOS 16 arriving later this year.