Dear Gurang,
Besides what our friend Mr.KK!HR replied in general terms, I would like to be specific with reference to the basic principles involved in a genuine engagement of contract labor. Though I am not sure what your question actually means, the way it has been framed appears to me that you want to choose some particular 25 people among the contract labor supplied by the contractor for your house-keeping activities and remove them for reasons best known to yourself. Invariably, your question may also indicate that you want to reduce the strength of contract labor by 25 people. A frank answer from your end may help us respond to you appropriately.