If you have bought new sim from zong franchise or local dealer (in Pakistan) after registration it is not activated when 
You have to activate it yourself and have to wait for a while before your zong sim is activated.
How to activate zong sim
You need to activate this sim by the following way:
To activate your new zong sim simply put the sim in your mobile phone and dial 789 and follow this instructions.
This method will also work if you have ported or changed your network from:
- ufone to zong
- mobilink to zong
- telenor to zong
And any other cellular network in Pakistan to Zong.
Once you convert your number from one network to another, you’re issued a new sim that you have to use instead of the old network one.
The activation of the new sim takes couple of days (3 days usually). Therefore be patient before the new sim gets activated.
How will you know if the new sim has been activated? Well it’s simple, if your current sim loses its signals and shows no network, then it means it has been removed from the networks and now your number is ported to the new network. Simply put in the new sim and you will find it activated.
Let me know if you have any difficulty while trying to activate zong sim.