More than 10 per cent of respondents said they felt they were "mis-sold on what it offered", with many also complaining that the coverage levels were exaggerated and that ongoing costs were higher than expected, particularly when accessing data overseas or exceeding data limits.
Around half of those surveyed said that access to Wi-Fi hotspots should be included as part of the deal, and many said they were confused as to which providers offered this and which did not.
Another 13 per cent were frustrated that there was no returns guarantee if the service was not right for them.
"Across the industry there are too many customers whose mobile broadband expectations have been set too high and have then been disappointed," said Peter Rampling, marketing director at O2.
"This is a terrible shame given there are loads of people who are having a great time with mobile broadband."
In response to the findings, O2 has announced that it is revamping its mobile broadband model in the UK in a bid to make it easier for users to understand.