Bharat Sanchar Nigam [BSNL] — landline surrender, security deposit not returned so far

Address:

Kakinada, East Godavari, East Godavari, Andhra Pradesh

My landline [protected], account no.[protected], was surrendered in october 2019. Invoice no. Sdcap[protected] for october 2019, after deducting bill amount rs. 63.84, the refund payable is shown as rs. 2771.80. Even after a lapse of 5 months, the refund amount is not transferred to my bank account. I am at a loss to understand as to why bsnl being a public sector company doesn't bother to transfer security deposit amount even after 5 months.