Numbers starting 0843, 0844 and 0845 are non-geographic service numbers. Ofcom says organisations use them for sales and enquiry lines.
Ofcom allocates phone numbers to communications providers in blocks. The provider shown is the one Ofcom allocated this block to. It is not the person or business that called you, and the number may since have moved to a different network, because people can usually keep their number when they switch provider. Ofcom does not hold information about individual numbers.
A call to an 0843, 0844 or 0845 number has two parts: an access charge that goes to your phone company, and a service charge set by the organisation you are calling. Ofcom says the service charge is between 0p and 7p a minute and must be shown wherever the number is advertised. The access charge depends on your provider.