In a bid to kill some of the backlash aimed at Apple over the cost of upgrading to the new iPhone 3G S, the Carphone Warehouse is offering cashback for customers who trade in their old iPhone 3Gs.

The mobile phone retailer said it will give people £170 for the 8GB version of the iPhone 3G and £180 if they trade in a 16GB capacity model. Anyone with a first generation iPhone will receive £100.

However, customers trading in an iPhone 3G must buy themselves out of their O2 contract.

The Carphone Warehouse said the handsets will be sold via its website, or in-store where they must be traded in against another mobile phone purchase.