A research - conducted by Carphone Warehouse, across some 2,000 mobile owners - shows that half of mobile users didn't have a clue what the allowances of their contract were. A staggering 47 per cent didn't know how many minutes, texts and data their tariff allowed them.
By Carphone Warehouse's calculations, mobile owners could save an average of £194 per year if they switched to a more suitable plan for their actual usage.
That's a total of £5 billion which the UK is wasting on inappropriate mobile contracts every year, whether users are paying for too much allowance, or in some cases not enough.
For example, £170 million of that wastage is incurred by those who go over their data allowance for the month, being billed with penalty charges.
Many customes proved particularly clueless in terms of mobile surfing, not having any idea what a megabyte represented in terms of everyday browsing usage or sending emails.
Andrew Harrison, Carphone Warehouse chief executive, commented: "When the UK is facing one of the hardest financial times in living memory, it seems crazy that £5 billion is being wasted on phone bills."
"The cost of data charges is a growing issue and this is only going to increase as more people convert to smartphones."