It goes like this:
You go to answer your phone and as you do the "caller" hangs up so you return the call. The number appears to be ringing but you are already paying a premium rate. Or you may hear that the person you are after is being contaced followed by a ringing tone.
I just got caught out. I called the number (07034275886) back for a total of 36 seconds and have been charged 50p for the call which is to a premium rate number. I knew that 090 were premium rate but was unaware that 070 are also.
Let your freinds know and never return a call to an 070 number.
Just found more here:
http://news.bbc.co.uk/1/hi/business/1394978.stm