There are two methods of Network Lookup that you can take advantage via this service.
This will, based on Ofcom information, return information from the historical records of the number you queried.
If the number itself has been migrated from its original provider since being launched, this method would return the original telecoms provider and not the new owner, since this method only recognises the provider by the number range itself.
This method will perform a live check on the number you query, and will return the current telecoms provider that controls that number, even if the number was transferred to them from another provider.
This method is also required if you are performing a lookup on any non UK numbers.