0800 numbers are a type of UK non-geographic phone number where the receiver is charged for the call, not the caller.
Before the launch of 0800 numbers, Freephone calls were made by calling the operator and asking for a company by name. On 12 November 1985, BT launched “Linkline”, which included the introduction of 0800 as a new toll-free service which they called “Freefone”.
While 0800 was the dedicated direct dial freephone prefix used by BT, the prefixes 0500, 0321 and 0958 were used by other phone companies in the drive to offer free-to-call phone numbering services in the UK.
However, by the end of the 1980s, dedicated direct dial freephone prefixes had come into use: 0800 was used by BT, while the prefixes 0500, 0321 and 0958 were used by other phone companies.