Consumer Redressal

Dear sir,we are software service providing company,in patna we are working for school automation management system to implement software in to the CBSE affiliated school,e.g gyan niketan school is our client school is using our software around one year,they clear ower monthly contarct payment 37,848 for the month of novemebr,december 2013,and january 2014.february,march,april month payment they are not giving and ower service is continuing till date.according to our work agrement.how to get ower payment from gyan niketan school,kindly suggest.what is legal procedure to get back ower payment.