C172 pilot reported a CFIT event during flight while troubleshooting communication system. The pilot realized the low altitude and corrected.

Narrative

Having landed at the airport to pick up my personal private passenger from the nearby village; I found I had no cell service and was unable to reach the FSS or anyone else on the radio. I thought I might get either radio or cell reception in the air; so I took off. Still not reaching anyone in the air I decided to overfly the nearby village attempting to visually alert my passenger as he might see me fly over; or reach him by cell.As I flew over the village I visually maintained separation and an altitude of ~500 feet. My passenger was able to hear and see me; as well as receive the text I had earlier sent (once my phone got service while over the village); and I landed again to wait for his arrival at the airport.I did not immediately see any issues. There was no complaint and I did not feel I endangered anyone; having maintained sufficient airspeed and visual clearance. However; on reflection I realized I probably had been below the 500 foot minimum separation from buildings and people. I downloaded my track and viewed it in Foreflight; where I was able to more accurately determine what my elevation AGL had been. I found the underlying terrain had actually reduced my closest clearance to ~200 feet.I now realize that to be safe and FAA compliant I should give a generous margin for terrain clearance; and ideally plan farther ahead how to contact my passengers. If an overflight will be necessary; I need to know ahead of time the minimum elevation ASL needed over the village or town in question. In this case; it should have been above 850 feet ASL to maintain the 500 feet minimum separation.