The ACMA said the two companies have allegedly engaged in 'missed call' marketing and that these marketing activities are likely to constitute serious and extensive contraventions of the Spam Act 2003.
Following ACMA's intervention, the companies responsible have now stopped making these calls while the ACMA continues investigating.
'Missed call' marketing is the term that has been given to the practice of calling a mobile telephone for such a short period of time that the owner cannot answer the call.
When the marketer disconnects the call, most mobile phones present a 'missed call' notification with the marketer's number. The marketer intends that the owner of the phone will think they have missed a legitimate call and phone the number back, at which time they hear a recorded promotional message.
ACMA industry output division general manager Nerida O'Loughlin said it is similar to receiving e-mail spam which includes nothing except a link to a Web site.
"In many ways, it is worse, as the cost of marketing is shifted almost entirely to the target, and the method of communication is more intrusive," she said.
"ACMA has closely scrutinized the missed call marketing practice to determine whether it is in breach of the antispam legislation. We believe that it is, and would like to send a clear message to the public and the industry about the legality of this practice.
In the first and most prevalent example of missed call marketing, callers were told about a gift of mobile content that they could receive by calling a 1900 premium rate number.
In a more recent example of this type of marketing, callers were advised of a mobile premium SMS-based dating service operated on a '19' number.
Complaints can be lodged via ACMA.