Probably ios updates heated up some electronic components and affected the network circuit power chips. I noticed my phone start to heated up and the battery run off completely few hrs after No Service issue appear.

i just updated to ios 15, removed my simcard and insert it back. Still the same, “No Service”. So ios15 is not the remedy for this No Service problem. I am clueless because I already tried everything seems it doesn't resolve at all

Thanks for your feedback! Luckily I read your comment because I was desperately looking the solution to resolve this issue since updating my ios to ios 15 dont resolve the issue at all.