Explain to me how the £600 phone makes better calls, do you get through quicker, are the calls clearer.
Well elcheapo phone uses likely 2G. Decent phone 3G
The traditional (old) 2G phones used the Full rate (FR) and then Enhanced Full Rate (EFR) codecs. While they were good enough, later on the newer phones started using Adaptive Multi-Rate (AMR) codecs. 3G used AMR codecs by default. This results in better voice quality and clarity.
Plus 2G calls cost incredibly more than 3G. I get 3p per min with my 321 Pay as you go from Three. On 2G I think its something like 60p per min.
My advice would be to go and get a locked Grade B Blackberrry Curve from CEX for £25. Get the unlock code for it for 60p via ebay. And there you go (this is what I have done to get a second punting phone last week).