The German landline operator Yourtel has been fined €66,000 for ripping off hundreds of elderly Irish customers.

Following an investigation by industry watchdog Comreg, Yourtel pleaded guilty to 88 counts under the Communications Act for charging 560 customers for a service that was requested but not supplied.

The prosecution was described as "unprecedented".

Dublin District Court heard the customers had been poached from Eircom and although Yourtel did not transfer the service they billed for it.

They ended up getting double-billed and Yourtel threatened them with debt collectors, legal action and having their details sent to credit rating agencies.

The offence carries fines of up to €5,000 per offence.

After hearing a litany of examples where elderly customers had been pursed and threatened by Yourtel, Judge Flann O'Brien described the offences as "nothing more than deceit" and he imposed fines of €750 on each charge, totalling €66,000.

Speaking to reporters after the case ended, Comreg director Barbara Delaney said: "Comreg welcomes the District Court decision to impose 88 criminal convictions on Yourtel.

"Today's District Court fine of €66,000 is the largest fine imposed by the District Court following any prosecution case taken by Comreg.

"We expect that today's District Court judgement will finally bring consumers' issues relating to Yourtel, which first came to Comreg's attention in 2013, to an end."

The company, which has claimed to operate the lowest-priced landline calls in the country, entered the Irish market in 2013 and had pleaded guilty to 88 sample counts, out of more than 880 charges originally brought by the phone industry regulator

Prosecuting barrister Michael O'Higgins SC told Judge Flann Brennan that Yourtel effectively cold-called Eircom customers to offer them a "flat bill" telephone services.

The 24-month contracts were for calls only and they would still pay Eircom separately for the landline.

Mr O'Higgins told the court that mostly 78-year-old customers were affected, the average age of the customers involved in the investigation was 65 to 66 and the oldest customer to sign up was in their 90s and another customer had special education needs.

Yourtel had about 5,000 customers but Comreg had received complaints from 17 per cent of customers over a certain time period compared to less than one per cent for other major phone telephone service providers.

The company took "a very hard-line view" of customers who complained, Mr O'Higgins said. They were threatened with late payment fees, legal action, debt collectors and having their details sent to a credit ratings agency.

In evidence, Comreg compliance manager Miriam Kilraine said the case was "unprecedented". She gave a summary of the experience eight customers had with Yourtel when they signed up their €11, €13 or €23 a month packages with two-year contracts.

Stated on the back of Yourtel's bills was: "Double billing is not possible you cannot be billed by two operators for your calls."

However, the customers services had not been transferred from Eircom and Yourtel also billed them for a service it had not provided. Complaints to Yourtel led to technical explanations and were not resolved.

Ms Kilraine said 40% of Yourtel's customers have contacted Comreg about the company, adding that this was also unprecedented, while the average amount of customer complaints in relation other companies was 0.3%.

The court heard that Yourtel had been successfully prosecuted earlier this year on one count of billing for a service that they did not provide, which resulted in a €2,500 fine and an order to pay €10,000 in legal costs.

In 2015, it was given the Probation Act and ordered to pay €2,500 to charity for failing to comply with a request from Comreg.

It had also been fined €2,500 in 2016 for unsolicited marketing calls.

The court heard that the company has offered all the customers affected refunds, which came to €125,000. So far, €116,000 worth of their refund cheques had been cashed and fresh payments were being issued to customers who have yet to take the refund.

The court heard that the company registered in Ireland, but does not have offices here and uses a mail direct service, at Kill Avenue, Dun Laoghaire, Co Dublin.

Its base was in Germany and company director Marijan Vukusic provided an affidavit to the court apologising. He said the company had been over-zealous, but since June 2015 it had not sought new Irish customers and the company did not intend to recruit new business in Ireland.

Pleading for leniency, defence counsel Oisin Clarke said that the court had heard a "damning account" of his client's business procedures. He asked the judge to take into account the guilty plea that the prosecution accepted was useful.

Mr Clarke also said that Yourtel had paid €10,000 toward the prosecution costs.