Ringing the university, to ask them to decline my clearing offer .....HELPP!!!

I received an offer after much rejections for the subject of my choice through clearing!

I was told that I must accept the offer ASAP- I was told even waiting to accept the offer on the next day could mean that the offer could be gone-due to very limited spaces available !

I felt at that time I had no choice but to accept the offer, due to the heavy rejections !

I went on UCAS and added the University as my clearing choice! The University have yet to confirm this!

So now, I have seen my course offered through clearing further out than my preferred area, which I would be happy to go to!

So is there ANY possiblity that I could ring the University of my clearing choice and ask them to decline my clearing offer, which they have yet to accept???

Please HELPpPPPP!!!!