Do you have one of those 'Unlimited Local & National Calls' packages on your telephone line? If so, you may or may not realise that most telephone companies do not include calls to 0845 (so called "local rate" numbers) or 0870 ("national rate"), you will probably only find this out by looking at the very small print at the bottom of the advert.
Unfortunately most companies that you have to call use these numbers for their call centres, and make you think that they are saving you money by saying "calls charged at local/national rates". This is incredibly misleading, especially since these companies often leave you sitting in a queue listening to 'your call is important to us' for hours on end. To make matters worse, the companies often receive a cut of the revenue from these calls.
I've found a great website saynoto0870.com which has a searchable database of companies geographic numbers which you should be able to call for free using your inclusive call packages.
Yeah, Stick it to the man!