If you’ve ever returned from a wonderful foreign holiday only to have your memories tarnished by an unexpectedly large mobile phone bill, you’ve been a victim of Bill Shock.

Bill Shock can happen in the UK if you’ve used more data or minutes than your contract allows, but most of the time it strikes a few weeks after you’ve returned from that trip abroad.

At the moment, when you use your mobile abroad, you leave your home mobile network and use another one – a process called roaming. 

Roaming costs are typically much higher than the standard charges for calls, texts and especially data. Mobile data is what you use when you check your email, visit social networks like Facebook and use Google Maps - anything that involves connecting to the internet when you aren’t using wi-fi.

Seven simple tips for avoiding bill shock

Tip 1: Set a spend cap

BT Mobile lets you set a limit on what you spend outside your plan. To change your spend log on to bt.com/mymobile using your BT ID.

If you’re heading abroad, BT Mobile sets a default  limit of £35 on monthly data charges. So if you go away and use more data than you plan to, you can rest assured knowing the maximum you’ll have to pay is £35.

Or, if you’re really worried about spending money on data, you can set the cap to £0 and use wi-fi while you’re away instead. 

Roaming charges are changing on April 30th. Read more about the cost of using your BT Mobile phone abroad.

Tip 2: Check international costs

Before heading on holiday, find out how much calls, texts and data charges cost on BT Mobile.

If you are a BT Mobile customer, from April 30th the cost of making a call EU countries to a UK landline or mobile number will now be 4.3p a minute, receiving a call 0.9p and sending a text to a UK landline or mobile number will cost just 1.7p. 

Calls from countries outside the EU are more expensive. For instance calls to a UK mobile or landline from France cost 4.3p per minute from April 30th, but £1.40 from Australia.* Check out the BT Tariff list for a list of call costs.

Tip 3: Track data use

When you are abroad, keep an eye on how much data you’re using by heading to bt.com/mymobile or using the BT Mobile app. You’ll soon be able to see how much data you’re using, whether you need to buy an add-on and how much of the add-on you have left.

[Related story: How SIM-only contracts can save you money]

Tip 4: Use free wi-fi hotspots

BT Mobile customers get access to millions of free wi-fi hotspots abroad and in the UK. Look out for the BT Fon hotspot on your phone. Check out hotspot locations to see where free wi-fi is available before you go.

Tip 5: Turn off data roaming

If you're really worried about your bill, turn data roaming off and use wi-fi wherever possible. To do that:

In Android - go to Settings – More – Mobile Networks – Data Roaming and flick the slider Off.

In Apple iOS - go to Settings and flick Data Roaming to Off.

In Windows Phone - go to All Settings – Mobile + SIM - Data Roaming Options and select Don’t roam.

Tip 6: Cancel your stolen phone

Sometimes a surprisingly big bill comes when a mobile phone has been stolen and the thief has run up huge charges. Our default data cap is £35, so unless you’ve set it higher, you’ll be protected to this amount. There’s no cap on the calls a thief can make, so still make sure you cancel your phone as soon as possible by getting in touch with us.

Man sitting at desk looking at bill

Horror stories

Data is measured in kilobytes (KB), megabytes (MB) and gigabytes. Some things use more data than others, which many people aren’t aware of and have been caught out with high bills.

Downloading a four-minute song uses up about 4MB, a five-minute video comes in at 30MB and a 45-minute TV show is 600MB.

Because roaming data is generally billed per megabyte, there are some real horror stories about people who haven’t realised just how much they’ve spent until they got their bills.

  • In 2008, a solicitor watched The Apprentice and two other shows on BBC iPlayer in France and foundherself facing a £5,000 bill.
  • An Australian traveller whose phone was stolen in Europe faced a £270,000 bill when they got home because the time difference meant the theft wasn’t reported until the next day.
  • Bristol schoolgirl Casey Snook, aged 14, went to New York for five days and returned to a £3,800 bill after updating Facebook with photos of her holiday in the Big Apple.

Roaming charges have dropped over the last few years and the EU has ruled that they are due to be scrapped by June 2017. But this doesn’t apply to the US and not every EU country is covered, so it’s worth being aware of the above.

*Prices correct at the time of writing, but may be subject to change.