Source of Client for Call Center Busines

Hi,

My name is Rumman,I am from Sydney and willing to open a call center in bangladesh, I have a plan of 50 seats center initially, Could any one give me idea about how to get the clients for this business? Do I have to setup the whole business first and then look for client by my own company website, or you reckon to get client first, Do you guys have any idea how to get the potential clients? what are procedures to approach clients? As I havent done this is business before I couldnt show my experience in this field to attract client. So any suggestion from any helpfull person?

thanks

rumman