Someone give me a lumios device he has lost the Sim how do I Change it to my own number?

Hi Blessing, you will need to contact MTN support for them to change the Lumos device to your number, the consent of the first user may be required before the change can be done because the device is giving on lease agreement.
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