How do you spend £59.54 on holiday in less than 20 minutes with nothing to show for it? Receive an incoming call on your mobile phone.

During a five-week holiday in South East Asia, I used my phone on average every other day for five minutes. My final bill came to £644.84 - more than I paid for the air fare. My phone was using the cheaper network, Mobitel. But it would have made little difference using the more expensive network, Casacom.

According to my network provider, Vodafone, calls to the UK from Cambodia cost £3.18/min. But my service provider, Singlepoint, charged me an extra £1.50/min. According to research published in April by British telecommunications watchdog Oftel, ignorance of roaming call charges is common.

Its mobile international roaming research also found that nearly half of UK con sumers with a pre-pay mobile phone are unaware they can be charged for incoming calls. Oftel also found that less than half of consumers have tried to reduce their mobile bills when abroad. Oftel is campaigning to cap the cost of calls for mobile users in the UK and is targeting the amount the recipient network gets, which can be almost 70% of the total charge to the consumer.

Oftel's plans to cap "termination fees" could save consumers £800m over four years at a cost of £600m in lost revenues for Britain's big four networks. While Oftel is working to cap mobile calls and collaborating with the European Commission on roaming call charges, it has published interim guidelines to lower consumers' mobile bills. These include: · Change from pre-pay to contract
· Use international traveller services
· Divert calls to voicemail and do not access it, or get incoming calls barred
· Use text messages instead of voice calls
· Buy a SIM card from a local mobile operator
· Select a different network.

Perhaps Oftel should also advise consumers to choose their service providers with care. As my South East Asian experience showed, variation in network tariffs is not always reflected in the costs charged by the service provider. Oftel appears to have no specific commitment to challenge service providers over their roaming tariffs. It says roaming tariffs should be self-regulated through competition and do not have to reflect lower network charges.

"How they structure their retail prices is ultimately up to them," says an Oftel spokesperson. It says that the onus is on consumer awareness.

Based on its research for UK mobile users in the Republic of Ireland, Oftel found that the savings for switching from pre-pay to contract tariffs could be between 45% and 66%. It also recommended that regular visitors buy a SIM card for an Irish operator, which could save 50-70%.

A few networks do not support text messages for roaming users and, for most mobile users, barring incoming calls and not making calls are not practical options. Depending on the service provider, switching to a different network can be a convenient way to save money for travellers without a regular destination. A mobile phone will automatically pick up the strongest local signal. But this is not necessarily the cheapest option. It is possible to select another network through Call Settings and Network Selection on a mobile phone. Vodafone and T-Mobile (formerly One2One) users can select different networks but their pricing structures can be complex. 02 (formerly BTCellnet) and Orange have introduced flat rates and streamlined their cost structures.

A comparative search of the big four networks highlighted surprising differences in roaming tariffs. Orange is head and shoulders above in Europe at 60p/min for outgoing calls, and 30p/min for incoming calls. For the sake of simplified pricing structures, however, Orange users do not save money in the USA (£1.10p/min for outgoing and 55p/ min for incoming calls). Vodafone, via the Nextel network, charges 77p/min for outgoing calls, and 62p/min for incoming, although its prices are exclusive of VAT.

T-Mobile's tariffs are clear winners for UK travellers to Australia, where its network deal with Optus means that calls to UK landlines only cost 11p/min, while Telstra and Vodafone will set you back up to £1 per minute. O2 has low rates on its international traveller service.

This reduces standard outgoing calls from any EU country from 72p/min to 49p/min, and incoming calls drop from 80p/min to 23p. It costs £2.54 per month and can be subscribed to on a monthly basis. T-Mobile has similarly effective cost-cutting schemes such as its World Class service.

This will reduce a call from France made to a UK landline to 69p/min. Roaming calls are expensive because the network takes a cut, the recipient net work takes a "termination fee", and the service provider also wants to make a profit. Oftel argues that it has no control over mobile networks abroad. But pressure to cap prices will come from Europe. Mario Monti, the European Commission's competition commissioner, said in February that some operators were charging consumers far too much to use mobile phones abroad, and he called for a Europe-wide tariff for roaming users. Michael Tscherny, EC spokesperson for competition policy, says: "When there is a smell of collusion or potential cartel, then we take an interest. We are looking at the costs of roaming charges that mobile operators charge to each other when calls are routed over different networks."

Tscherny says the commission wants to find out if there are grounds to investigate two UK operators in particular. "In the UK, two of the mobile operators have a much stronger position than the others." The EC is due to publish preliminary findings later this year. But for the time being, Oftel is placing emphasis on consumer awareness to make sure that calls are not the most expensive part of a holiday to the south of France.

Tariffs
Roaming tariffs vary greatly. Here are some sample prices for calls to New York and Paris.

In New York, the networks Nextel, Bellsouth, Voicestream, Pacific Bell and PCS1 are available. In Paris, the networks are SFR, Orange and Bouygues Telecom. All operators stress that prices are only guides.

In some cases your service provider (when you don't deal directly with the mobile phone network) will add its charge to the network's price, and this charge will most likely be higher than the one listed below.

All the prices listed are per minute without any discounted tariff deals.

New York

Vodafone
Cheapest to UK: Nextel 77p
Cheapest incoming: Nextel 62p
Most expensive outgoing: Bellsouth £1.27p
Most expensive incoming: Voicestream £1.32
(Exclusive of VAT)

T-Mobile
Cheapest outgoing to UK: Nextel 77p
Cheapest incoming: Nextel £1.27p
Most expensive outgoing: Bellsouth 94p
Most expensive incoming: Voicestream £1.53
(Inclusive of VAT)

O2
Outgoing to UK: £1.36p
Incoming: £1.02p
(All exclusive of VAT)

Orange
Outgoing to UK: £1.10p
Incoming: 55p

· Orange points out that UK VAT is not applicable on calls made or received outside of the European Union

Paris

Vodafone
Cheapest outgoing to UK: Bouygues Telecom 72p
Cheapest incoming: All networks 66p
Most expensive outgoing: SFR and Orange 73p
Most expensive incoming: All networks 66p
(Exclusive of VAT)

T-Mobile
Cheapest outgoing to UK: Bouygues Telecom and SFR 48p (off-peak)

Cheapest incoming: All networks 76p (off-peak)
Most expensive outgoing: SFR and Orange 81p (peak)
Most expensive incoming: All networks 82p (peak)
(Inclusive of VAT)

Orange
Outgoing to UK: 60p
Incoming: 30p
(VAT inclusive)

O2
Outgoing to UK: 72p
Incoming: 80p
(All exclusive of VAT)