Following up to @nazzzz's reply, you should also check network strength (ookla speed test or similar), and re-insert or replace your SIM card, older sim cards have this issue of not connecting (I had this problem)
It sounds like your phone is struggling to maintain a signal indoors, which can drain the battery quickly. Try switching to Wi-Fi calling if available, checking for carrier settings updates, or testing with a different SIM card to see if the issue persists. If nothing works, it could be a hardware or network issue.
Sorry to hear that what u r facing.. sort of remedies been shared by others members and hopefully ur problem solve asap.. and hope u r not facing THE OTHER part of unsolve network issues where tried many step to settle but at the end stressed u out 😅
