Jonah Hill prank-called businesses to prepare for 'The Wolf of Wall Street'.

The 30-year-old funnyman - who plays Donnie Azoff in the new dark comedy from Martin Scorsese - has revealed he perfected his character's New York accent by spending 90 minutes a day calling unsuspecting companies who had no idea they were talking to an A-lister.

Jonah, who wore glaringly white prosthetic teeth for the part and developed a lisp due to the dentures, told BANG Showbiz: ''You could take them in and out. But I had a horrible lisp, so I had to talk with them for an hour and a half every day for a month ahead of time to nail the accent and get rid of the lisp. So I would call different businesses as Donnie and talk on the phone for an hour and a half every day.''

The Oscar-nominated actor also heaped praise on his co-star Leonardo Dicaprio for helping him be a better actor.

Speaking at the UK premiere of 'The Wolf of Wall Street' in London's Leicester Square yesterday (09.01.14), he said: ''He's brilliant. I think he's the best actor of his generation. To me, when you work with people who are that great they just elevate you to a different level.''

Meanwhile, Leonardo, 39, who also produced the flick, revealed how hard it was to get the passion project financed because of the amount of drugs, sex and wild debauchery featured in the film.

He explained: ''This was a very hard movie to finance from the onset. Not many studios are chomping at the bit to do an American epic with Wall Street in the title, let alone this which is sort of focused on hedonism, debauchery and excess. It doesn't have all the conditional things I think Hollywood films have, and for that reason I'm thankful to that people [we worked with] for being willing to take a gamble on a very adult American epic about the state of our culture.''