Source: As worded by Indian Railways, Government of India

Indian Railways has Special Cells functioning at the Ministry and Zonal level to deal with complaints regarding passenger amenities, punctuality and catering facilities. The details of these Special Cells can be ascertained from the respective Zonal Railways. Now Complaint Monitoring Cells have also been established at Corporate Office, Zonal/Regional Offices of IRCTC for Catering Services.

Note: You can file pantry service complaint at all India toll free number too.