I used to be very much into the "phone phreaking" world and the Magidial was never used by anyone, because it didn't exist. It was invented by a con-man called Martyn Fisher - probably sold a duff piece of equipment to people for a lot of money. There were many other devices that allowed free phone calls such as a blue box (which generated tones to allow you to jump onto an international loop and dial wherever you wanted) and a red box (which generated tones to make the operator think you put money in - demonstrated in the film "Hackers"), but these devices are pretty much long gone. More recently there was a chip you could install inside a Philips Diga mobile phone (and later the Philips C12) which allowed free calls, but this was due to a design flaw whereby the credit was stored on the phone rather than the network. Needless to say, this has all been patched ;)