If they thought that the end of the athan marks the end of eating, their fast is valid because they were ignorant of the ruling.

I wanted to ask if someone thinks that they can eat during Azaan till it finishes and wasn’t aware that they are suppose to stop eating Suhoor at Azaan or at start of Dawn. And later find out that thier Masjid gives Azaan at true Dawn,do they need to make up the previous Fasts ?