Block transfers before receipt

There was a post about the Central Bank of Egypt's initiative offering an instant machine for 510. I called the number of the representative, agreed with him, and he gave me the bank's number to contact. I transferred 510, and after the transfer, he told me I needed to recharge the machine with some balance. I said the minimum is 2000 pounds, but thankfully I didn't transfer anything else. In the end, they turned out to be scammers; there is no initiative or anything.