Hi Taiwo. sorry for the wrong data activation. you can contact MTN support, they will convert the data to Airtime for you if the data is not in use.
You can contact MTN Support via any of the channels below:
MyMTN App
Twitter: @MTN180 / @MTNNG
Facebook: @MTNLoaded
Instagram: @MTNNG
Live Chat: http://bit.ly/2OC5bHz
Email: customercareng@mtn.com
Call Center: 180 or +2348031000180 (if you are calling from abroad or another network)
WhatsApp: • 09033000001