PTCL doesnot provide turn key call center solutions! It can only provide bandwidth that you would need. You will also need a NOC/Call center license from them.
There are certain options for setting up an international call center. Youc an do managed or hosted.
Scale is dependedent upon the business you are looking to attract. 24 seats is usually considered a profitable number to start off with
There is a training schoold opening up in Islamabad for CSR training and management.
I have experience in setting up call centers and I am running one in Islamabad. Let me know if you need info or help.