Agency won't refund me - help!

we shall refund you (apart from the agency fee).

so basically, I won't be living in a house anymore as I'm moving to different unis. So, I found a replacement for my room and the agent said, once your replacement has given us all the money that is required, we shall refund you (apart from the agency fee). He said this face to face.

I was there when my replacement signed to the new contract and everything. He kept me in the loop about payments (as he was a flatmate). So he has paid off everything ages ago. About two months ago.

I phoned up the agency saying that I want my refund as he paid off everything. They kept giving me excuses like "the person you need to speak to is on the phone. I can get him to call you back".. They didn't do this and other excuses like "he's out of office, one site project, won't back until next week"...

Three weeks later, I phoned him and he said that they won't refund me as they tend not to refund, despite him saying to my face that I would get a refund. There is NO WHERE in the contract where it says they won't refund you if you break the claws OR find a replacement (I'm the latter). So if this is the case, that means they should give me a refund for the guarantor as I'm not living there anymore so it's stupid that they can't refund me.

What should I do? It's £250 I could have used to pay off my student overdraft too!

But surely a deposit is for the reservation of the accommodation, if you don't take the accommodation you lose your deposit. That's the whole point, like a deposit for a holiday, you change your mind you lose the deposit, it is your security that you intend to go through with the contract, you didn't so you lose the deposit?