Bharat Sanchar Nigam [BSNL] — non-refund of landline security deposit

I surrendered my landline telephone ([protected] installed at house 247/5 channi himmat jammu) on 24/08/2017. I also deposited the telephone apparatus with bsnl on 29/08/2017 so that no deduction on this account is made from the refund amount due. The refund cheque stated by the bsnl to have been sent on my address on 20/11/2017 has not actually been received. I have visited the bsnl office several times only to be told that bsnl has large number of such cases pending settlement. This suggests fishy despatch process of refund cheques in the bsnl office. Could you help me out of the difficulty.