Call me about a grant I feel like it was a scan

It is a SCAM.  They would ask you to sent THEM money - and you must apply for a grant.

Please help! I was scammed into giving 900$ away.

Unfortunately, that money is likely gone. You best notify your bank immediately and inform them you were cheated. Depending on how it was done, your most hope will come if the money was given by credit card. If you wired it to them, consider it lost. Very sorry for your loss.