Betfair have an extensive FAQ on their website which answers the most common queries customers have. For those that need extra support, Betfair's customer support hours are between 8am and 11pm and they can be contacted via live chat, phone, or Twitter.
FAQ
https://support.betfair.com/ap...
Live chat
Twitter
https://twitter.com/BetfairCS
Phone
0844 871 7000