The thieves, many of them teenagers, don't even sell the phones, using them once or twice before throwing them away.
Police believe many of the thefts are an extension of playground bullying.
New technology
In the future police are hoping to be able to use new technology to stop the thieves.
They think "phone bombing" may be the answer - where the mobile phone companies send hundreds of text messages to the stolen phone very quickly, making it unusable.
