I don't think IDP or most consultants even charge money for study visa. They work on direct commissions from colleges, so they mostly invest their time in candidates who they think will be successful in securing the visa. And I strongly disagree with the comment that people with graduation and significant work experience have a low chance of getting visa for diplomas and grad certificates. I, along with three of my friends had applied for study permit last year. All of us were not only graduates but held post graduate diplomas as well. We all had four years of work experience and had applied for graduate certificate programs of our interests. All of us were approved and I think it was only because our SOPs clearly stated our objectives. A good SOP can definitely reverse a rejection, especially because when you reapply, the officer is bound to read your complete application which he could have had overlooked the first time. Don't be disheartened and give it your best shot. All the best.