Best mobile service provider in Karachi

I live in Lahore and will be staying in Karachi for a couple of weeks, so I require a new mobile number. As I have not been to Karachi before or neither know of anyone who lives there I need help from forum members to provide details of the best mobile service providers in Karachi. I need a mobile connection which would have good coverage and possibly have good internet connection.

To be honest I think mostly all mobile service providers are good and cover many areas with good coverage. I have used Zong in Karachi and it worked quite well for me.