HOW TO CHECK IF YOUR SIM CARD HAS BEEN REGISTERED ( MTN, GLO, AIRTEL, ETISALAT )

This tutorial will show you how to check if your MTN, Glo, Etisalat and Airtel SIM cards have been registered. It is short and very straight to the point.
I kept registering this particular SIM but I kept getting message from MTN that I should register my SIM. I got frustrated at some point and called MTN Customer Care to ask them how I can check if my SIM has been registered. The solution below was given and it worked.
GLOBACOM

CHECK IF YOUR GLO SIM HAS BEEN REGISTERED!

Send REG to 3456 as a message. If your line has been registered, you’ll receive a message in this format

Your SIMCARD +2348071111111 has been registered. Thank You!

MTN NIGERIA

CHECK IF YOUR MTN SIM HAS BEEN REGISTERED!

Send REG to 789 in a message. After sending the text to 789 with your MTN SIM card, you should get a reply confirming or denying that you have been registered.
If your sim have been registered, you will get a service message saying:

2348121231565 has been registered. Thank you!

Where 2348121231565 is your phone number!
I will update you on ways to check if your Airtel and Etisalat SIM cards have been registered.
Now here is the update:
There is no short code to send a message to like that of MTN and Glo:

CHECK IF YOUR AIRTEL SIM HAS BEEN REGISTERED!

At the moment you can only verify by calling 111 on your phone or by sending an email to customercare@ng.airtel.com

CHECK IF YOUR ETISALAT SIM HAS BEEN REGISTERED!

For Etisalat, you can verify your SIM card registration status by calling 200 or sending an email to care@etisalat.com.ng