Methods, systems, and devices for displaying advertisements on mobile telephone devices at the end of a call to a pre-designated number are disclosed. In aspect a computerized method comprises determining that a telephone call has been initiated between a mobile telephone device and a second telephone device, determining that the telephone number matches a campaign telephone number stored on the mobile telephone device, determining a media object to display based on the telephone number, downloading the media object on the mobile telephone device, determining that the telephone call has ended, and displaying the media object on the mobile telephone device after the telephone call has ended.