It's not APSPDCL, its now APCPDCL
Its available on all 3rd party apps.
Now regarding cashback /discount,
1.Use rupay platinum debit card on amazon for bills upto 500 ( offer is 20% of upto 100)
2. Axis Airtel for 25% cashback upto 250
3. Axis ace for 5% cashback on gpay