Ooasis,
As everyone said no desi consultancies pay for whatever they do not owe. I bet that must be your pay that you are not aware of. Any way wait until they inform you that you have been overpaid before you initiate any return. Just my thoughts :).
I am in similar but opposite situation. I quit working with desi consultancy but they are not paying me my balance. On top of it they ran my payroll for the last month (I did not work for ) but never pay me. Now I have to pay tax for money that I never earned or was never paid. I emailed them to fix that but they never responded.
I hope we both are employed by same employer. For some reason if you are over paid they are even lol.

longHorn: may be your consultancy still  billing the client . 

nepasider: I think that's a good idea. I will email them so that later even if they come after me than I will have proof saying that I contacted them after I received the money.

long_horn: Yes, you're right. Like everyone says, no desi consultancies, in fact not only desi even nepali consultancies do not pay for what they do not owe. As they say, esp when it comes to money no one is your friend. So I am still furious about this. I still haven't got chance to go back to my pay stub and look for all the dates, which I will do soon and will decide. I feel bad for what your employer did to you. I hope we had a same employer too. But please don't come after me asking for your pay check hai :P hehe, just kidding .

 khuru khuru goji ma hale bhai go ni .. lai dheraii hero hunu pareko gadi ka kira haru..!!