Apple has just released the minor iOS 15.1.1 update for iPhone users.
You can download the minor update by going to Settings > General > Software Update on your iPhone.
According to the release notes, the update improves call drop performance on all iPhone 12 and iPhone 13 models.
iOS 15.2 is currently in beta testing and should arrive before the end of 2021. It offers new features App Privacy Reports and more.