Pure Pro RO service - Service Delay

My RO service is due, because water taste changed from normal to bitter, even you can't use for Food or drinking purpose, I called them on **st Feb'** to come for due service which was actual due in Jan'** as per contract, every day they are saying technician will come next day but they are not coming, everyday I am calling them for service, sending on WhatsApp message on their all number, but they are not responding, I visited their office, but they have changed their office from address mentioned in bill, now they blocked my number, if you call them for new number they will pick your call but not from my number. looking for solution