Why it's not so good to talk from overseas

The true cost of using a mobile phone abroad is revealed today.

Consumer groups say holidaymakers are being ripped off because of the huge and confusing variation in cost between phone companies and packages.

An Evening Standard inquiry shows some phone owners are charged almost £15 every time someone from home calls them for 10 minutes. A halfhour call home can cost up to £36.

People using prepay or pay-as-you-go are paying up to five times as much for some overseas calls as people on a contract.

Ironically prepay and pay-as-you-go are marketed as more manageable options, often used by teenagers whose parents are worried about call charges.

Our figures are calculated using the example of Greece but prices are similar in much of western Europe.

Receiving a 10-minute call from home with an O2 contract discount costs £2.80. Prepay O2 customers pay £14.90. A half-hour call to the UK costs Orange prepay customers £36. Orange contract customers pay ?21.

Sending 30 texts costs a Vodafone contract discount customer £10.50. The price on Vodafone prepay is ?14.70. Jon Corke, deputy editor of What Mobile? magazine, said: "It's simple for people to use their phone abroad but the cost is not made clear. It's a bit of a rip-off by the networks because they are not making customers aware of all the hidden charges."

And it often takes a couple of months for a huge phone bill to arrive, because of the delay as phone companies liaise.

"People get quite upset," said Mr Corke. "Considering people could be only just on the other side of the Channel- - closer than Scotland - the networks seem to feel they are free to hike prices right up."

Hidden charges, from an industry turning over up to £32 billion a year, include:

There are ways to limit costs. For three euros, buying a Greek SIM card makes all incoming calls from home free to the receiver - though that would mean changing phone numbers.

Which? magazine's Jenni Conti added: "Abroad, phones default to a local network, but not necessarily the cheapest.

"You can manually change it - contact your operator for a list of that country's tariffs."

She advised switching off voicemail: "People can always send a text."