IELTS exam in Karachi
There are two testing center in Karachi which are AEO and British Council. Both charge similar fee for IELTS exam.
AEO welcome IELTS candidates physically than British council. Like when you go for registration they hand you admit card right away without making you wait.
British Council, Karachi
On other hand, British Council who are lazy in registering students. They take up to 10 days mostly even more than that they will delay your confirmation of seat for certain dates. I think it is because not having shortage of management or gap of communication.
Choice is yours but i would prefer AEO as they do not let you down.