A virtual phone number is also called Direct Inward Dialling (DID) or access phone numbers. It is a telephone number but without a direct associated phone line. Generally, these phone numbers are programmed to forward calls to one of the pre-set phone numbers. These are called follow-me numbers, personal number or a virtual phone number. A virtual phone number works as a gateway between traditional PSTN phone calls and VoIP. Virtual numbers users might use their existing phone, without having to buy additional hardware, i.e. use the available software. Users can also set to forward calls from virtual numbers to different numbers depending on the day of the week and time of the day routing. For instance, between 9 to 5 on working days incoming phone calls will be routed to the user’s office, however, on weekends they will be forwarded to the user’s mobile phone. The availability of virtual numbers is subject to the regulations in the issuing country.