How can I unlink one of my mtn sim

Sin unlinking from nin to link other...

I bought a MTN sim card yesterday and I was told to insert the sim card to a phone at night. When I did that I now received a message to dial *853# which I did, and I was seeing...

How can I become an MTN SIM registration Agent . I have a Laptop

My mtn Sim got logn out from my WhatsApp and I don't know why, and I can't login back