Standard bank is Hacked

I received an email from standard bank about u rewards, after speaking to the bank they said they will send a mail about u rewards that we must go in and see how many points we have because we can use the points for petrol and other stuff. The email was opened the bank send a OTP number to cellphone that was entered and then there was transactions taken place on my account where all my money was transferred to another account. i phoned standard bank with in 10 minutes reporting it, they said we should never open emails and we should send it to them to confirm that its really form them, after telling us they will send a mail. This happened on Christmas day . They then opened a case i also opened a police case, the email that was send domain is registered to standard bank its all legit standard banks email, but now they can't give me my money back after it was not spam email or anything they where the one's that was hacked because how do they send OTP number to phone and after entering it all your money is taken. They even said they cant see to whom it was transferred, how can a bank not see that and how do they allow such larges amount be transferred its a business account how do they just let all the money be transferred without any red flags.