Almost half a million young people regularly struggle to pay their mobile phone bill or top-up credit, a charity has found.
Mobile phone costs are causing problems for a "significant minority" of 18- to 24-year-olds, with some missing payments and borrowing to pay their bills, National Debtline said.
About one in 12 (8%) of young people with a mobile phone contract have missed at least one payment in the past year and 7% of all 18- to 24-year-olds say they have borrowed money from a friend or family member to pay a mobile phone bill
On average, they spend £21.88 a month on their mobile phone but more than a quarter (27%) say their payments are more than they expected.
However, six in ten (61%) say they receive good value for money.
National Debtline said about one in 10 calls it receives concern phone debt, up from about one in 25 calls in 2007.
It has called for better support from mobile phone companies and Ofcom to help those who are struggling, including earlier intervention and greater use of repayment plans.
It wants providers to build budgeting tools and information on money management into their websites and in-store processes to help improve the financial decisions of younger customers in particular.
Joanna Elson, chief executive of the Money Advice Trust, the charity which runs National Debtline, said: "A mobile phone is often one of the first financial commitments that young people take on in their lives and the vast majority will do so without any problems whatsoever. However, for nearly half a million 18- to 24-year-olds, keeping up with the cost of running a mobile phone is a real challenge.
"Mobile phones are no longer just 'nice to have' but are an essential part of everyday life - and we need to make sure that anyone struggling to cope with this or any other household bill receives the support they need."