Here is my situation. Can someone please help me!

I joined Vodafone in December 2009 and have been really unhappy with the service I received. I always get connection errors and my phone keeps disconnecting with almost any phone calls. Additionally, I hardly ever get any decent reception. I spoke to vodafone and they advised me to turn off 3G, which I have, and its been better but still is problematic. Thing is... I WANT 3G ON. Its a Internet Tablet and I dont want to be browsing the web in 2G!!! I live in London, so I dont have connection problems in this City!

I have never gone over the 500Mb limit, and dont have a problem with this. So... Can I still cancel the contract under these terms?

Of course I would bullcrap and tell them that im unhappy with the contract changes, bla bla bla. So would this be a viable way of getting OUT of the contract???

If I send them this letter, and tell them that they violated their own agreements, would I cancel this successfully? What do you think? If I stop the DD, would they NOT come after me and charge me the full contract fees and so on?

Also would I get to keep my beloved N900???

Please help! I think this would be a great opportunity to get out of the crap vodafone contract I am on now, and move back to O2, but I am not sure if I should do this!!! I am afraid vodafone will come after me and sue me silly!

Any advice would be greatly appreciated!