After activating your new sim card, dialing 555, the mobile number is then given 30 days airtime. To avoid the sim expiring, a top up must be completed during that time. Your new sim will remain on the active stage.
It is important that you top up your Prepaid number so that it stays active on the system. Otherwise, the number will expire. Once the number expires, it will then be recycled.
To prevent your number from expiring, continue adding airtime to your number by topping up.
Please note that Credit U transactions are not counted as a valid top up