There could be a number of causes for an unsuccessful transfer of your mobile number, here are a few:

Incorrect Date Of Birth For A Pre-Paid Service:

The Date of Birth you have given us may not match the Date of Birth held by your previous provider for the mobile number you are trying to transfer. In this case, you will need to provide us with the Date of Birth held by your previous provider. If your mobile number was not Pre-Paid than we need to use an Account Number, you can normally locate this on the front page of your latest bill. 

Incorrect Account Number For A Post-Paid Service:

If the Account Number you have provided us does not match your Mobile Phone Number held with your previous provider, this will result in the transfer process failing. In this case, we would need you to confirm your Account Number with your previous provider before trying the transfer again. 

Un-Allocated Mobile Number:

If the mobile number that you are transferring does not exist, has been disconnected or is suspended, the transfer will fail. Sometimes, pre-paid numbers can be disconnected when they have not been recharged for a certain period of time. In this case, we can provide you with a brand new mobile number, woohoo!