how to fix "no cell coverage" battery problems on iPhone

My iPhone 15 with current iOS (18.3.1.) goes though the brand new battery using almost no apps in less than 12 hours. Battery metrics show 70+% of power was used for "no cell coverage". Spent hours on the phone with Apple support. Friendly but completely useless. Said they had no record of it being a known issue. An IT guy at work fixed it in 10 seconds. Turns out there was a second electronic SIM card (you can use as a temporary number when in a different country) with no number so it was constantly using power to search for a connection. The solution: settings->cellular->select the eSIM that has no phone number listed and delete it.