Can't login to wp-admin

Hi folks,

I’m a newbie and have quite a serious problem. I couldn’t access the Customise page (kept logging me out), and one post recommended changing the domain name in in Settings – General.

I did this and now can’t log in to wp-admin; it just takes me to the home page of my website. I also can’t access any other page. ??

This is where the problem gets worse… I can’t log into FTP FileZilla either anymore! I inherited this site, and have no contact with our hosting SP (the old admin didn’t know how to either).

Please help! This is really urgent as we have a charity fundraiser on Saturday, and people need to book via our website.

Thanks in advance,
Sam