What is the ruling on fasting people breaking their fast before the Adhan, claiming it is delayed beyond the time of sunset?

The legal basis for breaking the fast is the verification of sunset, according to the Prophet, peace and blessings be upon him: "When the night approaches from this side, and the day retreats from that side, and the sun sets, then the fasting person has broken his fast." So, whoever breaks his fast after verifying sunset, his fast is valid, even if he did not hear the Adhan (call to prayer).