One in six people who used their mobile phone on holiday in the past year have returned home to a shockingly high bill. One in four were charged at least £40 more than their usual bill. The good news is that from midnight the cost of some of these bills will be capped.
The bad news is that we have no idea what these caps are or where they apply - so we could still find ourselves faced with a horrifying bill.
The cap, which comes in tonight, is part of the EU's Roaming Regulations. It means the maximum charge for making a call should be 19c a minute (excluding VAT), while sending a text should cost no more than 6c and downloading 20 MB will not cost more than 20c.
Unfortunately consumers' association Which? identified a major gap in our knowledge about what is and isn't covered. Almost half of people they surveyed thought that the cap applied to all countries in Europe, but in fact they only cover those within the EU. This means those travelling to countries like Turkey, which are outside the EU, could be in for a nasty surprise.
Bill shockData roaming bills can be incredibly high. In April this year one woman was on holiday in South Africa when she decided to download a The Best of Neil Diamond to play at a party. She was charged £2,600.
In September it was the turn of a mum from south London, who was charged £20,000 - or £2,700 a day - for data roaming while she was on holiday in Turkey. She said the bill was largely incurred by uploading photos to Facebook.
Protect yourselfIf you are travelling overseas and you plan to take your mobile, it always pays to get in contact with your mobile phone provider and check what the rules are regarding calls, text and data in your destination.
You may be able to buy a package which will give you a certain number of calls, texts and data at a lower cost (although you need to be aware of how much is covered so you don't go over this accidentally); you can also cap the total cost.
Which? says this is a wise idea, because if you get a shock bill and you have capped your usage with your mobile phone company, you can refuse to pay the bill for any usage above the level of the cap. It added that 48% of people were unaware of this.
However, some companies will simply send you a text when you get near the cap, enabling you to opt out and carry on roaming. If you choose to do this you need to understand the implications.
When you travel you should consider turning off data roaming, so your phone will only connect to the internet when you are using free WiFi services.
If you are planning to use your phone a great deal, you may be better off buying a SIM for the country you are visiting. This will mean using a different number, but the costs will be much lower. Check with your phone company whether you can put the overseas SIM into your phone or whether you will need to buy a cheap handset overseas too.