If you are looking around “free calls to Pakistan” that is almost impossible, there is nothing really for 
free. But yes there are plenty of VoIP termination
competitors which can help. However here is some info from “evongetz” that may help you to try some cheapest way to calling Pakistan through SIP.
The Session Initiation Protocol (SIP) is a signaling protocol used for establishing sessions in
an IP network. A session could be a simple two-way telephone call or it could be a collaborative multi-media conference session.
The following Carriers give SIP accounts,
Send someone to their office and get an account, and configure it in your switch as a route, and start sending traffic.
The typical cost of this will be 1 cent a min ( 60 paisa per min to land line) to Pakistan.
The following companies give SIP accounts, and you can buy them, and configure them in your switch.
Wateen www.wateen.com
BrainTel www.braintel.net.pk
Telecard www.telecard.com.pk
WorldCall www.go4b.net.pk
Hazara Telecom www.hccnp.net.pk
Burraq http://www.burraqtel.com.pk
Soon Link.net, and PTCL. Wi-Tribe will also a good SIP player in Pakistan’s voip market, currently Wi-Trible launched Broadband Wireless internet. their slogon is “Online with no line”
Wateen and Burraq:
Get a Wimax box, and get a local phone line with it.
Then email to Wateen and ask them the sip password for it.
They will send you the SIP configuration, If they dont, search on google, on how to get out the sip password out of wateen box, u will find a LOT of links.
Configure this sip account in your switch as your route to Pakistan and enjoy the 60 Paisa a min or 1 cent a min service from them.
Here is also a direct person who can help:
Hi!
Terminate VOIP traffic on Wateen @ $0.02 Per Min, We will help you generate revenue in
the growing VOIP market for Pakistan.
You will just send it to our “HighlyIntelligent Routing Server” and it will be delivered to wateen.
Our device is the only one in market which have the ability to terminate traffic on wateen.
Thanks
Regards,
Robert Hill
VOIP Wateen Expert!
Contact US
August 28th, 2008 at 3:08 pm
My question, I want to use my Asterisk PBX server with Wateen, so my Asterisk PBX will be SIP client to wateen’s SIP gateway but I’ve some Autherization issues whether SIP authentication is just being fine. what should i try to register my asterisk server with Wateen telecom?
January 4th, 2009 at 3:16 pm
Dear Sir
i want wateen sip account and his setting please help me about this work
and reply to me as soon
Thanks
Habib
February 3rd, 2009 at 11:40 pm
Dear sir
we need know how these sip account works for termination i have internet bandwidth and i need 24 Sip Account to terminate my Voip Traffic
please guid me after taking sip account wat do i need to install in my computer for terminating
waiting for your reply
Regards,
Rehman Khan
Email : rehman.phattan@hotmail.com
February 6th, 2009 at 5:27 pm
Rehman,
Here is your answer:
http://www.syednetworks.com/?page_id=105&forumaction=post&forum=5&thread=304&start=0
February 23rd, 2009 at 10:27 am
Hello Dear,
Can you drop some lines to start communication, We are running VOIP Co. in
Kuwait.we want to terminate our calls to wateen, once We get your reply we
will move further for VOIP relation.
Best Regards
Ali Hussain
March 16th, 2009 at 5:24 pm
Ali,
Following steps may full fill your requirements:
1. Get a few SIP accounts from Wateen including
Wateen internet, because they will
not allow you to setup SIP account on a server which is running non-wateen internet.
2. Setup Asterisk server in Pakistan according to your SIP accounts numbers location, for example if you have Lahore SIP numbers then SETUP a server in Lahore. The gateway for this server will be Wateen CPE device provided by Wateen telecom
3. Terminate your International calls to this Asterisk BOX via VOIP and this server will terminate calls to anywhere in Pakistan with low rates
May 21st, 2009 at 12:35 pm
sir i wan the whole protocol detail used in wateen and their usage in wateen
June 7th, 2009 at 12:36 am
Hi I am living in UAE and wants to make a cheapest calls to pakistan, is
there any oppurtunity through wateen to make it? please define me. Thanks
June 7th, 2009 at 12:54 am
I am a Wateen WiMAX user.
I need to use my VoIP Service from softfone. But Wateen stop to use VoIP
service through Softfone. So how can I get my SIP Password of my VoIP Number.
August 5th, 2009 at 7:16 am
Hello,
I have an idea about what is explained above but i am unable to fully understand and setup that. Kindly Some one can help me to understand and setup the process i am willing to pay for your time.
Kind Regards
m.h.ali@hotmail.co.uk
Contact me Please
September 14th, 2009 at 12:44 pm
Could you please tell me what information you required to activate my wateen mumber in uae.
September 29th, 2009 at 9:05 pm
sir could you please let me know about your requrirements and procedure i want this service from kuwait to pakistan
November 3rd, 2009 at 7:39 pm
Hi i have an asterisk server here in my home, and i am already using a
wateen SIP account, could you please tell me how can i dial through my
asterisk extension on this wateen sip account? or if you have any other sip
trunk account ?
December 25th, 2009 at 12:23 pm
HI,
I HAVE A WATEEN CPE DEVICE WITH TELEPHONE SERVICE CAN YOU PLZ HELP ME ON
HOW TO GET THE SIP USER AND PASSWORD OF THAT AND HOW TO SETUP ON ANY SIP
SOFT PHONE AS I WANT TO MAKE CHEAP CALLS TO PAKISTAN.