Using your mobile broadband abroad for work or holidays can still land you with a big bill when you get home.
Three quarters of European mobile phone and broadband users are worried about the coast of using their service on holiday, the European Commission has revealed.
And just 19% of people using the internet abroad think that data charges are fair.
Neelie Kroes, vice-president of the European Commission for the digital agenda, said: "Telecom companies must listen to their customers. Consumers feel there is still much room for improvement, particularly for data roaming."
The Commission has been trying to cut the cost of mobile phone and mobile broadband roaming costs in the EU since 2007, when it first introduced a cap on the amount that could be charged for calls, texts and internet use abroad.
The rules were revised in 2009, with the European Commission forcing providers to put a €50 cap on
mobile broadband abroad - operators must also now send users a warning when they reach 80% of their data-roaming bill limit.
However, roaming can still be expensive and the European Commission said that 72% of people were still worried about the high cost of using their mobile abroad.
Michael Phillips, Broadbandchoices.co.uk product director, advised consumers to avoid using dongles abroad. "Even with the EU cap on roaming fees, the cost of using mobile broadband abroad is still high," he said.
"If you really need internet access while you're abroad, talk to your provider about a roaming bundle to cut the cost - or simply look for a local internet cafe," added Phillips.