Ruling on eating suhoor whilst the muezzin is giving the call to prayer

That
depends. If the muezzin is giving the adhaan for subh (fajr) (he is giving
the adhaan when dawn has really started), then you must stop eating and
drinking, because the Prophet (peace and blessings of Allaah be upon
him) said: “Do not stop your suhoor when you hear the adhaan of Bilaal, for
he gives the adhaan at night, so eat and drink until Ibn Umm Maktoom gives
the adhaan.” The basis for this appears in the aayah (interpretation of the
meaning): 

“and eat
and drink until the white thread (light) of dawn appears to you distinct
from the black thread (darkness of night)”

[al-Baqarah 2:187] 

If it is known that dawn
has come, even without any adhaan, such as when one is in the desert etc.,
when you see the dawn then you should stop eating and drinking even if you
do not hear the adhaan. 

But if the muezzin gives the adhaan too early
or there is any doubt concerning whether his adhaan has coincided with the
dawn or not, then you may eat and drink until you are certain that the dawn
has started, whether that is known from a reliable timetable or from a
trustworthy adhaan which is known to come at the time of dawn. In this case
(if the adhaan is too early) you may eat whilst the adhaan is being given,
you may eat or drink what is in your hand, because there is no certainty
that the adhaan is being given at the right time, rather it is possible.