'Eighty per cent off our comprehensive dental check-up! Press 'one' to hear more, press 'two' to talk to our executive, or press 'three' to never hear from us again!' Recorded sales messages - delivered at high speed through annoyingly high-pitched monologues - are now a mainstay of using a mobile phone in Hong Kong. Answered in Hong Kong, these unsolicited calls may be little more than a rude interruption. Answering overseas, however, involves expensive roaming charges. And pity users who ever press 'three' - the dentist may disappear, but they will hear more than they ever wanted to know about discount IDD calls and other 'once-in-a-lifetime' bargains. Spamming has evolved from e-mail and text messages to voice calls due to cost efficiencies achieved using an old technology called the interactive voice response system (IVRS). The technology has been widely deployed for public inquiry services such as telephone directory services and weather forecasts. Government departments and companies also use IVRS for preliminary screening to direct callers to the correct department. But advertisers have recently harnessed IVRS to generate numerous cold calls simultaneously and reduce the labour costs associated with human sales staff. IVRS has become 'outbound' in nature, used in telemarketing at volumes that amount to a nuisance, as these recorded voice messages fill up voice-mail boxes and can incur roaming charges. Last year, the Office of the Telecommunications Authority (Ofta) received seven complaints from consumers about these tactics, while the Consumer Council received 29 complaints relating to telemarketing, including IVRS spamming. In last year's consultation paper on how to tackle spam, Ofta said the necessity of including voice or video calls in the proposed anti-spam legislation was 'debatable', due to the higher cost of cold-calling compared to electronic messaging through e-mail or short text message. But IVRS arguably disrupts such logic. According to industry sources, the cost of making a sales pitch using IVRS is often cheaper than SMS, as advertisers purchase the service from IVRS solutions providers that have the necessary infrastructure in place to handle the simultaneous call volume, including a high-speed T1 leased line, a server with voice card and an ordinary telephone line. Advertisers are usually charged on a per call basis, but the total charge also depends on the complexity of the programming. Consumer profiles based on user selections during a cold call commands an extra charge. Based on 200,000 spam IVRS calls per month, the monthly cost to advertisers would be about $92,000, compared with $100,000 for the same number of text spam messages. But the advantage of cold-calling using IVRS over text messages is twofold, because the technique affords advertisers the opportunity to complete a sale immediately rather than adopting a wait-and-see approach. 'IVRS is more cost-effective for the advertiser because, with the amount of money they pay, they get a better, interactive response,' said a source. Secretary for Commerce, Industry and Technology John Tsang Chun-wah said the government was finalising details of an anti-spam bill to be tabled next year after consultation. As junk mail, faxes, text messages and multimedia messages are likely to be included in the legislation, Sin Chung-kai, legislator for information technology, said Ofta should include voice-spamming if it was to maintain technology-neutrality as the cornerstone if its regulatory regime.