Cannot receive calls ios 14.8.1

Hello apple community! Im having trouble regarding receiving calls from iphone 6s running on ios 14.8.1. I dont have this problem from previous versions then suddenly this problem came up. I did most of the solution that can be found on the internet, communities, and on yt but no avail. Ive tried inserting my sim card on other phones and it can be called. I tried reinstering other sim on iphone and unfortunately it cannot receive any calls. Anyone having the same issue or is this some software/hardware problem? I can receive texts by the way. Im also worried about some settings>phone settings wherein they just keep on spinning nonstop (call forwarding, call waiting, show caller id). Any tips or tricks on fixing this (if there is any) would gladly be appreciated! Thanks everyone!