Bharat Sanchar Nigam [BSNL] — delay in refund of landline security deposit

I have closed my telephone connection no[protected] on 8/1/2018, but still I have not received my landline security deposit of Rs.1309/- generated by BSNL itself.No dues are pending & all bills cleared upto 31/12/2017.From 1/1/2018 to 8/1/2018, bill is of Rs.191/- is generated & adjusted from security deposit of Rs.1500/- with BSNL. Hence refund of Rs.1309/- is due from last 6 months.