Brihanmumbai Electricity Supply & Transport Undertaking [Best] — best deposit consumer no.[protected]

I have disconnected my best meter on 29th may 2018 and since i have disconnected my meter and after it is best undertaking's duty to refund my deposit amount. However, when i asked best authorities about my deposit, they asked me to submit deposit receipt, which is 26 years back. On 30.11.2018 i had been in the office of best undertaking, tardeo depot, grant road, mumbai, when the concerned officer was on leave. Other officer gave me telephone no. Of the office and told me to call on that telephone no. However, i tried to contract them, the phone bell is ringing and nobody is lifting the phone, now more than six months i have been following with the best authorities for deposit. No positive response. Kindly do the needful.