The cheapest means of acquiring a business phone number is to opt for one of the online companies that offer phone numbers, both geographic and non-geographic. You opt for the number that you want, with the area code that you want and pay a monthly fee. With the cheapest package, all incoming calls will come to this number which you then divert to another landline or mobile phone. You can also set up a message for unanswered calls. However, with the cheapest package, when you call someone back it will be from the number of the phone from which you are calling. Step up the package to have a number that can be used for incoming and outgoing calls.