Indraprastha Gas Limited [IGL] — refund of security deposit

I have requested refund of security deposit vide e-mail (Dtd. 24th may 2018) alongwith all relevant documents viz. Sd acknowledgement slip, sd refund form, cancelled cheque and application for refund etc. With subsequent reminders, but till date the case has not been processed.
When contacted over phone every time the agency informs that they will process the case within a week but it seems do not want to refund the amount.