ok the problem is you ahve listened to a bloke that works in a call center.
just look around on websites like
www.fish4jobs.com www.employment2go.com etc. and see just how qualified you need to be to get a job answering a phone.
now... yuo understand your mistake now?
what you will have connected to is either:
o2's broadband wifi service (unlikely)
O2's GPRS/3G service (most likely)
this is where your charges are coming from, internet use using their services.
how can they charge you for using your own service, you alredy pay your ISP for that