This has happened with me as well, but I am still not able to apply promo-code. The strange part is - they let me buy a Coupon worth Rs 1 for Rs 15 Cashback on DTH/Postpaid, but when I apply, it gives me this error "Not applicable on your FreeCharge account"
I contacted Customer Care and they said the same thing - fraud activity etc. but I have done nothing of such sort, hardly Rs 10 - Rs 50 transactions. Lol.
Any idea by when will the account be back to be able to use Promo Codes again?