I dialed a toll-free number from a payphone and was instructed to deposit 50¢. Why?

By law toll-free numbers dialed from payphones are, as their name suggests, supposed to be free for the person placing the call.

If you attempt to call a toll-free number and hear a message saying to deposit coins it probably means you called a number on one of the newer toll-free exchanges, and the phone has not been programmed to recognize the new exchange as toll-free. So the phone thinks you are dialing a long-distance number. Many phones around the country were never programmed to recognize toll-free numbers starting with 1-855, 1-844, and 1-833. All payphones should recognize the older toll-free exchanges 1-800, 1-888, etc.