0800 numbers are free to phone for the caller and since 2015 have been free to call from both landlines and mobiles. So they are essentially paid for by businesses and organisations to incentivise people to call a number, by making it free. For businesses, 0800 numbers are rented on a monthly basis, with calls being paid for (by the business). This per minute call charge differs according to factors like, where the caller is, and whether they have called from mobile or landline.