How to stop MTN NG Message on my phone. It is disgusting and disturbing. Pop on minute by minute is not good

Hi Emmanuel, click on the SIM Tool Kit on your phone, select MTN MsgXpress and MTN Link Up, if any of them is on, you can put it off.
You can dial *447#, *700# and *123*5# to see and deactivate all unwanted VAS (Value Added Service)

If the issue persist, you need to activate Do Not Disturb (DND) service.

Do-Not-Disturb (DND) is a service that allows you to stop /opt-out of receiving promotional messages on 3rd party services like Bulk SMS, VAS promos, etc. The DND service can be activated by sending HELP to 2442 for free and is available in two modes:
• Fully Blocked Mode – Allows you to opt out totally from receiving promotional messages via SMS and IVR. This can be activated directly by sending STOP to 2442.
• Partially Blocked Mode – Allows you to filter specific service categories of promotional messages to be received. This mode will block ONLY THE CATEGORIES you selected and can be activated by sending the specific number of the option(s) to 2442