Both system failure and human error can result in bigger mobile phone bills, writes Jamie Smyth

Taking a mobile on holiday is second nature to most Irish tourists these days, with texting home from a Spanish beach now a more popular pastime than volleyball.

But, as 100,000 Irish consumers have found out in recent weeks, taking a mobile phone on holiday can also be a confusing and costly experience for consumers.

Never mind the almost impossible task when travelling of working out the best "roaming rates"  among the scores on offer. Now, consumers have to check they aren't being ripped off by firms incapable of totting up their bills.

Over the past two weeks, the two biggest Irish operators, O2 Ireland and Vodafone, have both admitted overcharging some of their customers for calls made or received while travelling abroad.

Following an enquiry made by The Irish Times, O2 released a statement blaming a billing system error for double-charging 70,000 subscribers who received calls when travelling in Europe.

Ms Danuta Gray, O2 chief executive, said last week that it had charged users €500,000 more than it should have, due to a software glitch that caused it to charge two rates to customers.

"We have moved to a new, tiered roaming service... the software that we are using failed to switch from charging the old rate to charging the new rates. Instead it charged both rates."

This double-charging, which affected contract customers and not pre-paid subscribers, was detected in April by O2 during a standard internal systems check, according to the firm.

It says it will repay users by late July.

O2 said it implemented a software patch to fix the problem the day after The Irish Times reported on the overcharging.

However, the firm refused to comment this week on the particular software problem and why it took two months to fix a problem that was first discovered in April.

It said it would wait until submitting a report to the regulator later today before talking further about its mistake.

O2 uses a billing system provided by the US software firm Amdocs - the world's biggest billing system company - to mediate its roaming call charges.

The computer system includes a rating engine that looks up and selects the correct rate for calls. This rate is taken from a large selection of tables of rates that have to be written into the computer system manually.

The entire billing system can be made up of 100 million different lines of software code and mistakes do happen, according to Mr Enda Hardiman, of the Dublin-based telecoms consultancy, Hardiman Telecommunications.

"Billing systems are areas of very great complexity, particularly as new services such as roaming and data services are introduced," he said.

"But one would hope that the companies do extensive testing to make sure this type of thing doesn't occur."

Perhaps the biggest surprise is the length of time it took O2 to fix the problem, says Mr Hardiman.

Vodafone blamed its recent three-week period of overcharging on human error rather than a system fault. However, the consequences for its customers were similar: bigger mobile bills.

"This was primarily due to the miscoding of new Vodafone roaming rates in the billing system. This was the result of a human error which was identified as part of routine control checks," it said in a statement.

The error led to an extra charge for VAT being added on to the customer accounts of about 20,000 Vodafone subscribers. The total amount of overcharging amounted to more than €100,000.

Undoubtedly, human error played a role in Vodafone's bout of overcharging - with a simple inputting mistake causing customers to be charged incorrect fees for calls. But the fact that the error was not picked up for three weeks suggests the firm does not have adequate testing systems.

Mr Gerry Fahy, Vodafone's director of strategy, says the system is fine but the processes used to introduce new roaming tariffs were not robust enough.

He said in the future Vodafone would put in place an extra check on its systems after inputting a set of new tariffs or information.

Ironically, Vodafone contracted Accenture last year to upgrade its testing systems in the area of revenue assurance (a division in which Vodafone Ireland plays a key role for the group).

The complexity of roaming rates - Vodafone had about 1,300 different tariffs up until March 2004 - undoubtedly makes it difficult to detect errors quickly. But clearly, Vodafone and O2 did not properly test their computer systems before rushing to launch new roaming tariffs in March.

The spate of overcharging incidents at the two biggest Irish mobile operators has caused the third operator, Meteor, to review its own internal billing systems.

"At the time of the O2 incident, we did a cursory check of our roaming system but we did a far more detailed check when the Vodafone overcharging incident occurred," says Mr Andrew Kelly of Meteor. "This took about seven hours because we had to check all our roaming partner agreements all over the world."

He says the firm, which has more than 200,000 customers, is confident that its systems are not overcharging its subscribers.

But international examples of overcharging suggest that it is a widespread phenomenon and something that is not often picked up by individuals.

A recent article published in the Australian Financial Review claimed that companies are regularly charged too much in bills.

AAS Consulting, an Australian group that analyses corporate telecoms spend, said that, after benchmarking more than 100 corporate firms' telephone bills in a given year, it had never found one that was absolutely right.

"The telephone bills of big companies are so complex - they're delivered on CD ROMs - that many don't realise they're paying way too much. Most bills are incorrect and have significant billing errors," said Mr David Swift, head of AAS Consulting.

So, if one lesson should be learnt from the recent overcharging episodes, it is that no billing system is foolproof and future errors will occur. Clearly, the media and the communications regulator will have to keep a sharp eye on the mobile phone operators to ensure they are not short-changing their customers.