A new service has been launched in Sydney which promises free telephone calls to 70 international destinations simply by calling a local mobile number.

Callforfree.net.au allows people to dial into a local mobile number then enter the country code and phone number of the international call.

The call to the dedicated mobile number is then transferred to Callforfree.net.au's Sydney data centre and then routed over the Internet using VoIP and terminated in the destination country.

Callforfree.net.au managing director Sat Pal said the service only took three days to set up and already has about 100 users.

"It can scale up to 10,000 users and then we would need to do a big chunk of investment with a telco to expand it which would cost about $500,000," Pal said.

No additional SIM card or phone software is required to use the service.

The customer gets charged their standard local call rate to the dial-in number and from then on the international call is free.

Callforfree.net.au makes money on the margin for call termination charges and there is no time limit on calls; however, not all countries include mobile numbers and most only calls to landlines. For the complete list see this PDF.

"It's ideal for students in Australia wanting to call home cheaply and for people who want to use more of their mobile phone cap allowance," Pal said, adding the call quality equivalent to a standard mobile or landline.

The service is available to all mobile phones on all local carriers except Optus and its resellers TPG and Virgin Mobile.

Telstra, 3 and Vodafone mobile phones can use the service for free and no registration or contracts are required.