iPhone 13 Battery Draining

Apple wants me to go to Best Buy for a diagnostic test (which I will have to pay for). This test has been run four times in the past two weeks. They are telling me nothing is wrong, clearly there is ! I have watched my battery go from 100% to 89% in 4 hrs. This has been going on for two weeks now. I do not have Apple Care, nor do I want it. It is way to expensive. I had this issue approximately four years ago (just like everyone else), it was determined that Apple had to replace batteries! This is happening again. And yes, I have everything shut off on my iPhone 13, nothing is running in the background. I need to know what other folks are experiencing and if they were able to resolve this issue without paying a lot of money. I do not want a new phone, I just want this one to work ! (And yes it is paid off).

[Re-Titled by Moderator]