HTC One S Phones 4 U price

[YoshikiUK]

Hi, i have been browsing for mobile phones on a contract and noticed that whereas the HTC One S is on quite an expensive contract direct from Orange and Vodaphone etc (£31 per month), from Phones4U it is listed as £15.50 on Orange's Dolphin plan?

Just wondering why it is this cheap on Phones 4 U? Is there a catch, or anything different from getting a phone direct from Orange?

Thanks for the help.