+290

Country Code: +290
International Call Prefix: 00
Trunk Prefix: 0

Ascension Island no longer shares the same country code with the rest of Saint Helena (i.e. Saint Helena and Tristan da Cunha).

Format: +290 XXXX

From 1 October 2013 all existing 4-digit telephone numbers on St Helena will be prefixed by a ‘2’ to implement a 5-digit numbering plan. The change in numbering resulted after the increased demand for new telephone services while also providing a platform for the future introduction of a cellular network on the island.

Although Tristan da Cunha shares the +290 code with St Helena, residents have access to the Foreign and Commonwealth Office Telecommunications Network, provided by Global Crossing. This uses a London 020 numbering range, meaning that numbers are accessed via the UK telephone numbering plan.

...
Wikipedia