Mainly aimed at telecom security managers. Monthly A neat-o magazine that covers technical issues of the telecom industry. Very professionally done. The publishers of Teleconnect also run Telecom Library. They publish several books of interest to telecom enthusiasts.
Telemarketing covers just that.
It's the bible of the industry. TRAC is a non-profit that publishes a the above newsletter, which tracks rates of the major ling distance carriers. Both residential and business editions of the newsletter are available. They cover news about the collectible pre-paid calling card industry. FREE Sample upon request.