iOS 15.1.1 Prevents Dropped Calls on iPhone 12 and iPhone 13 - TidBITS
Apple Iphone 12 Pro Max iOS Version 15.1 RC 256GB 6GB RAM Gsm Unlocked Phone Display 6.7 inches (1284x2778) Processor Apple A14 Bionic (5 nm) Front Camera 12MP Rear Camera 12MP +
Apple Releases iOS 15.1.1 With Call Improvements for iPhone 12 and 13 Models - MacRumors
Apple Releases iOS 15.1.1 to Fix Call Drops on iPhone 12 and iPhone 13 [Download] - iClarified