There are VTU(Virtual top-up) service providers that buys data from MTN and sell it to people who wants to resell(resellers) or directly to customers at affordable prices...
You can convert your Airtime back to cash. Check mansub.com.ng they are legit site into vtu business. You can likewise get data and Airtime at affordable rate.
How To Get 2GB For 200 Naira – MTN Night Plan
Dial * 406 #
Respond by pressing 3 to select the MTN nightlife plan.
Then answer 2 to select 50 nairas for the 250...
