It should be obvious that this is a SCAM.
If they were genuine, they'd ask you to sign a document saying you'd only keep the 30%, and then send you a cheque/bankers draft.
NEVER give your Bank details to someone you don't know!!!!!!!!!!!!!
After all, you wouldn't just give your credit/debit card number over the phone/web to an organisation you'd never heard of, would you???
Or how many of us would!!!!!!