How can I get refund of data to cash because I mistakenly buy data of 20000 instead of 5000

Hi Adebisi, to reverse wrong amount recharge or subscription to your bank account, you need to contact your bank or your point of purchase with the details of the transaction like reference number, amount, date of purchase and channel of activation, your bank will then send the reversal request to MTN.
But if you want the data to be converted to airtime, you can contact MTN support, they will help to convert the data to airtime if you have not used the data.
You can contact MTN support via any of these 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