₦3500 for free on the network. Here are the procedures:
- Dial *447#, and then call any network for at least 2 minutes.
- Then dial *446# and you will be automatically credited with ₦3869 valid for Airtel-Airtel lines only.
You can use *123*9# 2 to check your remaining balance.
I think it's a glitch so you should probably use it while its still hot.