02 Ripping me off, what can be done?

I wanted to up grade my blackberry for an iphone three months before my contracted was due to end the lady in the shop told me it'll be £60 to finish my contract. When i rang them to cancel it was actually £120 to pay so i went back up the shop to return my iphone and say i'll wait in till my contract ends because it was too much money. The assistant manager said he'd credit my account £100 so all i'll have to pay is £25. Well i'm out of my 14 day "change of mind period" that o2 offers and he still hasn't credited my account after many phone calls. So i'm paying two contracts.
Can any one tell me my right?

Should've just upgraded your first contract

O2 are not ripping you off, you didn't check the terms of cancelling your contract and now are paying the price. As said you should have upgraded your old contract.

2 things
- how long did they say it would be till you got the 100 pounds credit.
(and why is it not in cash in the shop anyway?)
- what proof/witnesse do you have that these offers were made.

Technically, the way the 'upgrade' was being done was to
- buy out the original contract (expected at 60 pounds but turned out to be 120)
- start a new contract (same phone No?) for the iPhone - I assume to get a deal price?

The manager has now offered you 100 pounds towards the 120/125 on the old contract, it is still presumeably going through the system?

You expected to pay 60 pounds to pay off the old contract (yourself)
You will soon end up paying only 25 pounds… When the 100 comes through.
Sounds like a really good deal.

So all you need to do is confirm how and when the 100 notes will arrive.
Or has the shop already cancelled the 1st contract for you, and paid off that bill?
The 1st contract by now should have been cancelled - formally to reduce the charges (that is probably why they expected it to be 60 pounds but 120 if you kept paying it)

You need to find how the shop intended the 100 notes to come to you. I
(it can take up to a month for the internal billing departments to work their magic)

And get it in writing!