Dear Imran,
To my understanding there are a few requirements for a call center setup.
1. You need a PTA license to operate a call center/VOIP. The license is free of charge. You might want to check the PTCL and PTA website for more information. To my knowledge the license/NOC from PTA is free of cost.
2. To operate a call center you need to acquire the bandwidth from PTCL. They are offering you Full Ciruits.
3. Only if you need to go VSAT you will need special permissions.
I hope this helps.