Update Carrier version (bundle) without updating iOS
I have iPhone 5S A1457 with iOS 8.4.1 and Carrier 20.0. Yesterday there's LTE network started working in Belarus in band 3 (1800 MHz) - supported by my phone - but it can't register, only 2G/3G is working.
I tried my SIM card with iPhones on iOS 9.2 and Carrier 23.0 - everything is OK. How to force update Carrier bundle without updating the entire operating system? I tried to connect device to PC and open iTunes but there's no prompts for update the carrier settings. Even after resetting to factory settings. Also I can't find links for *.ipcc with a latest version to update Carrier manually through iTunes.
iPhone 5s, iOS 8.4.1