Hi Shiva,
I think you are providing security personnel on contract basis as per schedule of rate as in agreement and you are trying to convince your clients for enhancement in schedule rates. If yes, can you tell me what are the terms & conditions pertaining to 'revision of rates' of schedule as per existing agreement, is there a clause providing for escalation/revision of rates? If so can you extract here for my ref. If there is no such clause, it's better idea to personally meet the concerned in your client cos with a request letter(s) justifying your request, and repeatedly try. I afraid very few only would act on such matters simply on an email from a service provider like you. Above all it's mandatory to ensure payment of minimum wages of the relevant category, that's the responsibility of both the PE & Contractor.