Bharat Sanchar Nigam [BSNL] — Non refund of my security deposit upon surrender of my landline phone-reg

I have surrendered my land line phone no[protected] on 12/7/2016 at the bsnl telephone exchange office at sirpurkaghaznagar, dist. Adilabad, telengana.
I have not received my security deposite so far even after lapse of more than eight (8) months. I request bsnl authorities to refund my deposite at the earliest please. The necessary bank details i have alredy submitted while surrendering my land line phone at sirpurkaghaznagar
From,
D. T. Choudhari
Cell no - [protected]