By Matt Cole
There has been a rise in the number of mobile phone accounts being cloned or taken over by criminals, figures show.
According to the UK fraud prevention service Cifas, the practice is one of the growth areas of identity theft.
It has seen a 74% rise to 633 cases in the first half of the year, compared with the same period in 2008.
After obtaining personal details by theft or deception, the fraudsters can add additional handsets to accounts and use them to run up large bills.
Cifas members include banking, insurance and telecommunication firms.
Richard Hurley from the service said: "In the first six months of 2008 we had 364 proven cases of accounts being taken over, and 899 by the year's end.
"In the first six months of this year we've confirmed 633 cases.
"It is an area where the increasing sophistication of technology makes mobile phones a status symbol and therefore a boom area for fraud."
He said its latest figures may represent a fraction of the problem's true scale as Cifas members only file cases of confirmed fraud, not suspected cases.
Many mobile phone operators will send new phones anywhere requested by a customer and account holders can often be unaware their identity has been abused until they notice increases in direct debits.
The Mobile Data Association says there are now 65 million handsets in the UK.
While that gives fraudsters a vast number of potential victims, Cifas says most attempts do fail.
But when criminals do succeed in cloning an account serious problems can follow.
It happened to Rik and Aimee Brown from March in Cambridgeshire.
Tattooist Rik explained: "We both [have] got phones, so were supposed to have two lines, but months later I was doing all my end of year tax paperwork and found a third with some other woman's name and address linked to it.
"But it was coming off our direct debits."
Aimee, 26, added: "I had noticed my direct debits going up and up, and at first I just thought I was going over my monthly plan, or that the kids were using the internet on my phone so I kept paying."
The couple are still trying to sort the issue out with their mobile phone provider.
Victims can face the tricky task of explaining to their service providers that they have no knowledge of fraudulent activity. Worse still, they may need to repair a negative impact to their credit rating.
Experian, one of the UK's three credit reference agencies, says it has seen a rise in the number of people seeking to repair bad credit scores caused by fraudsters.
Experian's Consumer Education Manager James Jones told Newsbeat: "We can help, but it can take time to remove. Usually it takes about three to four weeks, but in some cases it can take months.
"That can be a real problem for people if, for instance, in that time they are trying to take out a mortgage."
Mr Jones added that while most fraud is spotted at the outset there are simple steps people can take to protect themselves.
"The best way to avoid being a victim is to take care with your personal data. Check all your bills very carefully, and if they don't turn up chase them up."
The main mobile phone operators Vodafone, O2, 3, T-Mobile, and Orange say they take security very seriously and encourage customers to take care of passwords and other vital personal details.
Most have information on their websites about how not to become a victim.
Mr Hurley from Cifas said: "When disposing of documents such as mobile phone statements, make sure they're shredded.
"Make sure they are unreadable because if personal data falls into a fraudster's hands, anything can happen."