How can I retrieve airtime sent to a wrong number through share and sell

Hi Oluwafemi, you need to contact MTN customer care for them to reverse the airtime to your line if the wrong number has not used it.
Kindly find below MTN Nigeria Contact Channels.
1. MyMTN App
2. Facebook: @MTNLoaded
3. Instagram: @MTNNG
4. Live Chat: http://bit.ly/2OC5bHz
5. Email: customercareng@mtn.com
6 .WhatsApp: 09033000001

Hi Oluwafemi, MTN can help you to reverse the airtime to your line if the wrong number has not used it, you can contact their support for assistant.
You can use any these channels to contact them:
1. MyMTN App
2. Facebook: @MTNLoaded
3. Instagram: @MTNNG
4. Live Chat: http://bit.ly/2OC5bHz
5. Email: customercareng@mtn.com
6 .WhatsApp: 09033000001