Prefixer allows you to quickly add prefixes to numbers in your address book. It creates new entries for all of your contacts, or for contacts that you choose, without deleting any existing information. For example, you can add a calling card number before dialling out a contact's regular number to save on long distance. When travelling, you may want to dial an access number before the number you wish to call; Prefixer is perfect for this kind of use. When you're done travelling, simply delete all the prefixes the app added with one button tap! Because the prefix is stored as an additional field in your contact, you can call through with the added prefix without returning to the app, making for a clean, built-in solution that you can use in the Phone app, Contacts app, or even with Siri!