The process of porting is designed to reduce the duration you'll be without a service. Once you've provided your new network with the PAC code, your previous number will stay operational, so you can continue to receive calls and messages.
However, during the actual transfer of the number, your service might experience a brief interruption. When this occurs, it should merely involve switching off and rebooting your mobile device for the complete service to be restored.
By following these tips, you can easily obtain a PAC code and switch mobile networks while keeping your phone number.