The telephone directory enquiry service 118 118 met regulators yesterday after admitting staff had been sacked for giving out wrong numbers.
The telecoms regulator Oftel and the Independent Committee for the Supervision of Standards of Telephone Information Services (Icstis) are investigating allegations that 118 118 staff deliberately give out wrong numbers and cut customers off so they can finish calls in less than 40 seconds and qualify for bonuses.
A spokesman for The Number, which runs the 118 118 service, said 30 staff from call centres in Cardiff and Plymouth had been dismissed. He added: "We have a bonus scheme that has three principles, only one of which is the length of the call."
Rob Dwight, a spokesman for Icstis, said, "We have taken action against directory enquiry companies in about seven cases for breaches of advertising and imposed fines of up to £15,000.
"These services can only operate with our consent and we have the power to withdraw their permission to operate. That is not likely to happen in this case but it is the ultimate sanction."