Battery Drain for new iPhone 13

Hi,

I have a problem with draining battery charge.

I bought an iPhone 13 a few weeks ago, but it had a draining battery problem after upgrading it to the latest iOS version, 15.2. It has lost its charge so fast that I should charge it several times a day.

I had done all the techniques that save battery charge, but none was helpful for me.

I have upgraded my phone to the last update of iOS 15.2.1, but I still have that problem.

I don't know what I should do now. It bothers me, and I am going to regret buying this phone.