@Maha,
Well I would like to suggest you also consider the option of 'BETS' while taking the decision of selecting a preparation academy for IELTS. I have many case studies that reflect that an average student can take IELTS Band 7.0 or above by smart tricks offered by 'BETS' during IELTS preparation.
In addition to that If you are comfortable with your English speaking skill set you can also opt for Self Study. Like "Cambridge Practice Tests for IELTS" series 1-4 help you a lot for IELTS preparation.
For general IELTS details you can log onto;
http://www.britishcouncil.org/pakistan-exams-ielts.htm