Unable to get back my R3000

Good day sir/madam, I was called to open up a LUNO account and said I would be introduced to Bitcoin. They directed how to open up an account they gave me all the instructions over the phone on how to open up the account. I did and when I asked to withdraw I couldn’t. This is plain rubbish I have the screenshots to prove I did not make any transactions on my account. When my son tried to withdraw the funds when I showed him I bought Bitcoin he said it is a scam . Please assist me in getting back the funds. I would like this to be investigated.