How can I get out of a mobile phone contract?

[OC25]

I have been contacted 2 months ago to go back to a previous mobile phone provider. During the call the sales person mentioned that T-mobile would be able to match my actual offer (previously descibed by me) for a cheaper price, including calls, texts, and internet illimited ... and that they'll provide as O2 was doing before, an international service ... all this for a price of £41, ...
1/ After a couple of weeks I realized being in France that I had no international service. So I called and reported it, they said that they were gonna sort the problem out and that it'll cost me an extra £5,... I agreed to it even though that was already a change compare to whaty was said on the phone.
2/ 2 weeks after the suppose date the internaitonal booster was suppose to kick in, back in france still no coverage, I called them and still no booster, but they said they will remedy for the same price already mentioned on the first call.
3/ Back in France last week still nothing, so I called today and still nothing but they mentioned to me that I have to place a £100 or maybe £150 deposit for the international booster to kick in (first time I hear about that, obviously never mentioned on the phone when they tried to gain me back).
I asked to talk to a manager but obviously they were all in a meeting. I told them to give me a call back during the day as I wanted to have a word with somebody in charge. And that I wouldn't have a problem switching provider again (as it has been mentioned on the phone that I could cancel my contract anytime) if needed as i felt they made me take a decision that was uninformed, that a large part of the element were missing. Here is my surprise too, I can do it if I pay the cancellation fee of £700, something ...

I feel this all story is a joke, as to me, I have the feeling I have been mislead into a contract that doesn't correspond to what was presented to me on the phone during the sale call. If I would have known all this, my decision would have been completely different.

What can I do about that?

[knowabit]

Did you actually sign a contract??

[factor-fiction]

The difficulty may be proving that they agreed to include the same level of international service as you'd had before. Did you receive a contract to check?

[lcg]

did you read the contract when they sent it to you? if not, then you are in a world of trouble. go back to the document or ask them to send you another copy....and take things from there. you could try to just cancel and not pay, but for £700 they may well issue bailiff/court proceedings against you. get hold of the contract and start things from there.

[sunny-dave]

Did you get a new handset as part of the new contract?

If so (even if you can persuade them to release you from the contract on the grounds that it was mis-sold, which I doubt after a couple of months) you will have to return the handset.

Get them to review the recordings of your sales call and the complaint calls - you may be able to persuade them to honour the original offer.

[OC25]

@ knowabit I didn't sign a contract as all was done through the phone.
@ Icg76 I actually think they were no contract joined to the shipment of the new phone.

and I forgot to mentioned that it took more then 3 weeks to receive the phone, they had to make another shipment so just because of that problem I was of the usual 2 weeks concellation period.