MNP enables a subscriber move from his service provider (donor) to another (recipient) without losing the number he/she already uses (eg change from MTN to Glo Mobile without losing his/her MTN number).
When you request to change your service provider, the recipient provider
will issue you a new sim card but you will still retain your phone
number. This simply means a subscriber can keep his/her phone number
when changing from one service provider to another despite the change in
the SIM card of the subscriber.
For you to understand the processes involved in MNP, you have to familiarize yourself with the terms below:
==> Port In: joining a new service provider
==> Port Out: leaving a service provider
==> Subscriber : The customer that owns the number to be ported
==> Recipient: The service provider that a subscriber is changing to
==> Donor: The service provider a subscriber is changing from.
If subscriber A wants to leave MTN for Glo Mobile, it means subscriber A is porting out of MTN and porting in to Glo. MTN in this example is the donor, while Glo Mobile is the recipient.
If you want to change your service provider, you will have to visit a recipient operator
via one of its points of sale such as office, friendship centre, high
street store, corporate sales team, or authorised dealer. For example,
if you want to change from MTN to Glo, you will have to visit a Gloworld
outlet or a Glozone shop to request for MNP.
When you get to the office of the recipient, you will be issued MNP request form to fill. You must have a valid proof of identity with visible photograph, your SIM must be ACTIVE, you must be able to provide the serial number of your SIM card and you must have registered the active SIM card.
A new SIM of the recipient provider will be issued to you and the SIM will be registered at the office. You will be informed to text "PORT" to 3232. If you fail to send the text, the request will not be honoured.
The recipient provider will forward your request to NPC (Number
Portability Clearing House ) where validation will be carried out. If
validated OK, the SIM will be activated and you will be informed.
Once your new SIM is activated, any airtime you have left on your old
SIM will be wiped off and calls you make thereafter will be billed
according to the default tariff plan of your new service provider BUT
your phone number will still remain the same.
NOTE: You can only change from one network to another once in 90 days.
Culled from http://www.ogbongeblog.com/2013/03/mobile-number-portability-in-nigeria.html