MCI Communications Corp has followed US Sprint Communications Co in saying it intends to pitch for a big bite of the US public pay telephone market, where AT&T Co has been stripped of its monopoly. MCI will be promoting its MCI Card long distance credit card, and operator-assisted services as well as offering substantial commissions to owners and managers of facilities where public pay phone service is available. Under the new rules, pay phone owner-managers will be sent ballots, allowing them to presubscribe to the long distance carrier of their choice with random allocation of all the don’t knows.