Mobile phone users could incur heavy charges just by having their phone switched on abroad, according to uSwitch.com - and could get into debt as a result.
22 million holidaymakers will take their phone abroad this year, but 15 million will not check the cost before they go, according to the report.
Aside from the cost of making phone calls and sending texts, an increase in the number of phones with an always-on internet connection could mean users incur expensive data charges.
A debt expert at Think Money said that using a mobile phone abroad can prove costly, but there are things people can do to avoid this.
"If you want to use your phone abroad, it`s a good idea to contact the network provider beforehand to check exactly what the cost will be. This makes it easier to budget for the additional cost.
"Some network providers may offer packages that reduce the cost of using a mobile phone abroad, while other companies offer SIM cards specifically designed to make it cheaper."
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