I run an international call center in Islamabad. I will strongly recommend that you do a very thorough study of the said subject.
It is great that you are interested in this business. But this is not an easy path. Setting up a center is the easy part ; running it effectively; achieving profitability and attracting long term customers/clients is the difficult part.
Operations, technology setup, bandwith, LD, co-location, business development, marketing and HR ; all these issues are full blown subjects of study in context to call centers.
Take your time studying the market and the works. Write a very solid business plan and then hop on the bandwagon.
Good luck to all well wishers of pakistan.