At first glance Oh-say-yah. That’s more to do with I tend to read things like that in Spanish. Or, maybe Oh-see-yah. Then I’d move to guessing Oh-she-yah, or Oh-Chee-a. So many possibilities.
Know the background of the person would help with the guessing. It’s like pronouncing Marcia, Irene, Guy, Claudia—it really matters what country they are from, and how the person chooses to pronounce it. Even names that are common can be be pronounced different that what you are accustomed to.