Spectranet — company not giving the refund of deposit amount

Address:

494, Ist Floor, CMH Road, Indiranagar, Bengaluru – 560 038, Bangalore, Karnataka, 560066

I have initiated the disconnection of spectranet internet connection on 2019 april 20 and they collected the device by first week of may. Also told me that, i will get the refund within 24 hours. I waited, waited and waited, finally got one mail in july saying that, due to bank issue they are not able to transfer the money and need a cancelled cheque leaf. I sent a new mail with the requested details on the same day itself. And after that i was in regular contact with them. But they are not providing any resolution and just giving some silly excuses. How i can tackle this problem. My account id is 172740.