The time for Suhoor (sehri) is until Subah Sadiq. Once Subah Sadiq begins, the time for Suhoor ends and the time for Fajr prayer begins. Therefore, the criterion for ending Suhoor is the end of the time, not the Azan. The Azan is called at different times in different places. Therefore, it is necessary to stop eating and drinking as soon as the time for Suhoor ends. It is not permissible to continue eating and drinking during or until the end of Azan. Therefore, a fast (Roza) of such a person who continues to eat and drink in Ramadan during or until the end of Azan after the time for Fajr prayer has begun, whether intentionally or unknowingly, will be invalid in either case. Rather, it will be obligatory for him to Qaza (make up) that fast (Roza) later.