Using a mobile phone aboard can lead to a huge ‘bill shock'

Even if you don't plan to make calls while abroad, uSwitch.com, the independent price comparison and switching service, warns that the minute consumers switch on their phone abroad, it will register onto a local network. This means any activity on the handset will be billed at overseas rates, which are much higher than standard charges in the UK. Charges could include paying up to £1.50 per minute to receive calls, which is free within the UK, or £1 to send a picture postcard SMS from Australia which costs a maximum of 37p in the UK. Other charges could be incurred for someone leaving a voicemail message, and to pick up voicemail messages - which in the UK cost just 21p a minute at the most.

And those with smartphones or internet-enabled handsets need to watch out for sky-high data roaming charges. These are often included in monthly packages in the UK, but can be as much as £3.07 per megabyte in the EU or £8 per megabyte in the US or Australia. With the increasing use of smartphones and the potential danger of data roaming charges the EU introduced new measures to prevent ‘bill shock' for consumers using their mobiles to browse the internet while abroad. Consumers have been able to set a financial limit on their roaming bill, with a €50 limit automatically imposed. But this is only put in place for travellers within the EU - so anyone travelling further afield remains at risk of limitless bills.

Over the last few years the EU has made great strides in lowering the cap on how much networks can charge for people using their phone overseas. However, even if usage is carefully controlled consumers can still suffer a ‘bill shock'. One of the best ways consumers can save money is by signing up to their network's roaming package. Three and Virgin don't offer a roaming package, but O2, Vodafone, T-Mobile and Orange all do. Vodafone's ‘passport' package is free but T-Mobile, O2 and Orange customers have to pay up to £5 per month.

But by spending just a few extra pounds travellers can get access to even greater rates, which in the long run should save them coming home to find a huge bill on their doormat. If you are travelling to the US for example, an Orange roaming package can save you 30% on calls made to the UK for just an extra £5. Likewise, travellers going to Spain who use a lot of data, could opt to pay £3.06 to reduce data roaming charges by 74% from £3.07 per megabyte to just 80p.

However, even though the cost of these packages may seem low, for those who don't use their phone much abroad it may be more cost-effective not to take the package. It's important consumers consider how they use their mobile phone abroad before signing up. For example an O2 customer travelling to Australia would be better off taking the package if they made just 6 minutes of calls to the UK, and if they were heading off to Spain they would be wise to invest in a bolt-in if they're likely to make 20 minutes of calls. But Orange and T-Mobile customers would need to make 34 minutes of calls from Spain to make the roaming package worthwhile.

Ernest Doku, technology expert at uSwitch.com, comments: "Contacting your mobile network should be high on every mobile user's holiday checklist, alongside packing their passport and sun cream. Using a mobile phone aboard can lead to a huge ‘bill shock' when you come back home, but if people stay in control and make sure they are getting the best rates they can avoid getting burnt. Opting for a special roaming tariff, fixing a cap or even using a cut price local SIM card can help to keep bills low. At the very least, ask your network to switch off your voicemail service before you leave the UK to avoid these hidden charges.

"But today one of the biggest ways to get stung is by the high cost of data roaming. Mobile internet users must ensure they check that this is turned off when not in use to prevent online services such as email updating automatically. They could also try to avoid visiting sites that are heavy on the visuals, as data is charged per megabyte downloaded - although this may be a hard ask for the Facebook and Twitter addicts amongst us."

Savvy consumers can avoid returning home to an unwelcome bill by using uSwitch.com's mobile do's and don'ts:

Switch off your voicemail service when you leave the UK and switch back it on when you get home - call your provider to do this

Switch off the data roaming option in your phone settings - or ask your supplier to switch off the voicemail  and data services for the duration of your break

Ask your provider to cap data roaming charges to an affordable level

If you have an unlocked phone, then buy a local SIM card when you arrive for local rates

If you know you will be calling home while away, look into buying an international PAYG SIM, such as Truphone

Speak to your mobile phone provider about overseas charges - you may be able to switch onto a cheaper roaming package

If taking your phone for emergencies only, switch it off before you leave the UK and only switch on if needed while away, as charges can rack up every time you turn the phone on

If you want to keep in touch, consider texting rather than calling - it's far cheaper

If you are a Pay As You Go customer, make sure you have sufficiently topped up before you travel

If travelling with someone else, consider taking just the one mobile between you.