Restart Your iPhone
Restarting your iPhone can fix many issues, including reception. Powering your iPhone off and then turning it back on may help refresh its connection to the nearest cell tower.
If your iPhone has a SIM card, you can try removing it, making sure it’s clean and not damaged, and putting it back in. That won’t be an option if you’re using an eSIM instead, and models of the iPhone 14 and later sold in the US only have eSIM cards rather than SIM cards. However, since these are embedded in the phone and soldered right onto your main circuit board, they can’t get dirty or have problems making contact the way a physical SIM card can.