For ECA you have;
World Education Service (WES) - It takes too short to send you the report but your university in Pakistan should be in their list.
International Credential Assessment Service of Canada (ICAS) - I do not know the procedure
Comparative Education Service (CES-UoT) - It takes 15 weeks to provide you with the ECA and as I used it so I can describe you the whole procedure:
Getting your Documents attested from HEC
Go to your university and ask the admin to "verify" your original degree and transcript (on back).
Fill an online HEC form by signing up and get the form printed.
Carry the aforementioned form, original degree(s) and transcript(s) along with the colored copies (front and back) to HEC Regional Office near TV Station (if you are in Karachi). You have to go there early in the morning to come back early. They will take 5 days to return you the documents, in the next window get them in the sealed envelope.
Now make another envelope and put the following:
Your identification copy (passport first page preferable).
Your HEC sealed envelope.
CES form (which can be downloaded from CES website).
Send this envelop by courier to CES address on website.