Some directory enquiry services charge up to £23.97 for a call lasting less than a minute. Some callers, making longer calls, have ended up paying as much as £350.
Source (which is two years old):
https://www.bbc.co.uk/news/business-39842723
Calling directory enquiries is usually madness. As others have pointed out, you can search online for free. If you must call a directory service, use Gingejbee's link to call The Number (either free, with advertising, or for just a quid without the ads).