If there is no Kohen (Cohen) present in the Synagogue at the time of the reading of the Torah, in Sephardi Synagogues, a Yisrael is called in his stead for the first Qomah ('Aliyah) which is ordinarily read by the Kohen. The second portion which is ordinarily given to a Lewi (Levi) when a Kohen went up for the first portion, must also be given to a Yisrael, as is mentioned in the Shulhan 'Arukh.
In Ashkenazi Synagogues there are different opinions. There are many who do send up a Lewi in place of a Kohen when there is no Kohen present, whereas others send up a Yisrael. In any case, Ashkenazim are permitted to send up a Lewi for the Kohen's portion when there is no Kohen present, since this is the ruling of the Rama in his glossary on the Shulhan 'Arukh.
(See Shulhan 'Arukh 135:6 with Rama)
See what people are 
