British phone retailer Phones4U unveiled a new six-month upgrade plan today designed for Brits who want and can afford the latest and greatest handsets. Just Upgrade My Phone (JUMP) helps customers split the cost of a phone and monthly bill over separate two-year contracts, allowing them to upgrade as often as every six months, but there is a catch — it's not as simple as it seems.

JUMP lets you trade in an old device to offset it against the remaining balance of your contract. As an example, Phones4U explains that if a customer takes out a £37.99 monthly plan with JUMP on a non-iPhone device, this cost will be split into £15 for the carrier charges and £22.99 a month for the JUMP service agreement. After six months, the customer can then upgrade to an iPhone 4S by trading in the old device at £175 and offsetting it against the remaining balance for the JUMP service, resulting in a new commitment of £58.44 per month. The new charge is based on the remaining balance (£238.92) split over 24 months (£9.95), and then added to the monthly cost of a 24-month iPhone JUMP plan (£28.49 per month) as well as carrier charges (£20 per month). Customers can also choose to keep the old device but this will obviously affect the new commitment price.

Phones4U says it will assess the price of trade-in phones, but that it guarantees devices will be worth at least £100 for the first 12 months. Customers also have the option of trading in two more phones alongside the contract phone during an upgrade phase. The attempt to simplify contracts is noteworthy, but the process feels overly complicated among a carrier market vying for your attention, and we see the potential for arguments over a phone's worth, especially based on its condition. Either way, Phones4U will launch its new deal at all 586 UK stores, online, and via telesales by May 2012.