Brits collectively wasted a stonking £811m in the last 12 months on unnecessary costs on top of their monthly mobile tariffs, a study by price comparison and switching service uSwitch.com has found.
More than one in four (42 per cent) British mobile users paid out an extra £39.72 per year on unforeseen mobile charges.
The study found that exceeding mobile data limits (39 per cent) was the most common reason for out-of-tariff charges as users were stuck in wrong deals for internet browsing.
Premium rate calls and texts increased phone bills for almost almost a quarter (23%) of mobile customers while roaming charges for using handsets abroad hit 20 per cent in the pocket.
Over a third (37 per cent) didn't know the difference between SMS and MMS messages, costing almost a fifth (19%) of mobile users in additional charges.
The report claimed that switching to a better mobile tariff for your needs could save you an average of nearly £100 a year.
Read more: Why it's time to put your smartphone down
Ernest Doku, telecoms expert at uSwitch.com, said: “The really frustrating thing is these charges could easily be avoided. Billpayers are spending three quarters of a billion pounds on out-of-tariff charges, suggesting many people are languishing on the wrong mobile deals.
“Smartphones have made us all hungrier to surf, stream and search online and exceeding your data limit is the biggest culprit when it comes to excess charges. Only 14 per cent of mobile deals sold through uSwitch.com offer unlimited data, which suggests people are still underestimating their data usage.
“Getting your tariff right plays as much a part in keeping bills down as understanding any hidden costs. If you’re not sure where you are overpaying, look at your bills over the past 12 months and see where your usage is heaviest. This will help you work out where you are being caught short."