I have actually confirmed with my client and they said that my employer(contracting agency) has already charged them for my salary. But now my contracting agency is withholding my salary without giving any explanation or answering any emails.
But have you sent the registered letter as suggested ? You need to start somewhere. How long has it been in reality ?
As I understand you were contracted or employed by a recruitment/contracting agency (don't start me on those) to perform duties for a third party (your client). Your client paid an agreed amount for the performance of your work to your contracting company. Your contracting company has an agreement with you to pay you an a pre-agreed amount for possiby a pre-agreed job (ie you were given a specific task to do in a specific timeframe).
Now are you a contractor or an employee of the contracting company ? There is a big difference and you need to read your contract. You and your client may be under the impression you were a "temp" but in reality you might be considered "an independant contractor" commonly referred as a freelancer.
If that is the case and as a worse case scenario ; because you did not finished your pre-arranged task they have no obligation to pay you !
You need to read your contract as well as all annexes word by word. Suppositions and impressions do not stand up in court. What does is facts ! Obviously it would be better to avoid court and lawyers due to the high cost.
Cheers