Hi Ubido, the issue will likely be a system glitch, you can contact MTN customer care for possible resolution.
You can connect with them via any of these channel
1. MyMTN App
2. Facebook: @MTNLoaded
3. Instagram: @MTNNG
4. Live Chat: http://bit.ly/2OC5bHz
5. Email: customercareng@mtn.com
6 .WhatsApp: 09033000001