RIYADH, 10 June  — A senior official at the Saudi Telecom Company has denied subscriber claims that some of them could breach STC’s surveillance system that restricts family mobile phones to eight predetermined numbers. STC has installed a secret device in its billing system to interrupt a number called illegally from a family mobile phone.

Saleh Al-Jaser, STC’s director of marketing administration, said the company was not aware of any such foul play. He said STC had installed an advanced and efficient system to detect any tampering with its code mechanism that regulates the numbers used by family mobile subscribers. The accounts committee issues reports of all calls made by the subscribers, the official said, adding that a comparison between the permitted numbers and the mechanically-recorded numbers by each user helps detect any tampering which is strictly prohibited.

When the service was launched, STC had warned subscribers against misusing it. Anyone found infringing upon the system will be asked to pay the difference between the connection charges for the ordinary cell phone and the family mobile, the company said at the time.

STC issued the warning when some bills of family mobile phones began recording numbers which they were not allowed to call.

But subscribers claim that the latest method of hacking STC coding is so ingenious that the billing system will not record or identify the violation even if the surveillance system detects it.

STC sources said such an illegal system, if any, would not be attractive to subscribers as the difference in connection fee between the ordinary cell phone and the family mobile was not worth risking a penal action. The present fee for an ordinary mobile connection is SR800 and for a family mobile it is SR400.

Al-Jaser also denied that users of a particular brand of mobile phone can use the SMS service without being billed with the help of a code, circulated via a website. The STC’s rate for short messages is 30 halalas per minute.

Al-Jaser said it was only a ploy to trick customers and said manufacturers of the particular brand might have used this to promote their product.