If you need to talk to someone at Bulb, you’ll need to contact them directly - see https://help.bulb.co.uk/hc/en-us/articles/115001240291-How-can-I-get-in-touch-with-Bulb- for their phone number, live chat and email address. This is a community forum for members to help other members (okay, occasionally, Bulb staff do make ‘fly-thru’ visits, but they guarantee to read every thread).
That is a very high bill and I would have expected something to catch it… Is the bill estimated or is it based on two different meter readings provided by yourself?
When you manage to get this resolved with Bulb directly, would you mind letting us know how this happened just so we know for the future? Personally, I think a transcription error occured when a meter reading was supplied (perhaps a gas meter reading was entered for electric or vice-versa, or a mis-keypress changed a reading from 1234 to 4234 or something) - however, I would have still expected those to be caught as ‘out of range’ through the meter validation process.