You should follow your people who sight the moon in your country and not follow Saudi Arabia

In our country Bangladesh the Ramadan starts after one day of saudi arab and my friends are saying that Ramadan should start with same time in the whole ummah like since the people of arab saw the moon first as a one ummah we should start withthey say anywhere in the world if the moon is seen we should start fasting…….now im confused what should i do ??? should i start with our local people or with them???