Just like Mtn double data offer,
Airtel is doubling data for all their customers who subscribed for 3.5GB data using their REDHOT promo. This message was sent to me by Airtel official which I believe was also sent to some Airtel users which says;
"FREE 3.5GB Bonus waiting for you & a chance to WIN 10Mill in the AIRTEL REDHOT promo! Dial *437*2# and activate 3.5GB and get EXTRA 3.5GB for N2000/val/30dys"
As shown below;
This implies that if you subscribed to 3.5GB data plan with just 2,000naira that you will be given extra 3.5GB and that's will be making 7GB for 2,000naira.
I think this is a cool offer from Airtel.