Ofcom records show that numbers starting 07566 are allocated to Telefonica UK Limited. Note that due to number portability if an individual number has moved to a different operator this information is not publicly available.
Ofcom's last recorded change for this number range was March 2009.
The correct way to write telephone numbers beginning 07566 is in the format 07566 xxxxxx
For more information on tariffs and usage of numbers starting 07 please visit the page on 07 numbers