Changing of Last Names

Hello,

I am hoping someone is able to help me with a family research issue I am having. We have always known our ancestor's name is Jacob Phillips. A lot of the of the information I have coincides with Byron Whitesides's info. When I look in the Russian Orthodox records, my family is listed a Potorochin and not Phillips. I have also found census document showing their last names as Alugli. Does anyone have any insight on to why last names have changed over time and why during the same time frame I can find all these different last names for the same people? When looking at Kodiak birth and marriage records my family is Aleut and Creole. Any insight would be very much appreciated!

Kristy