Kaspers Zukovskis, 20, first targeted the 19-year-old victim while he was sat inside McDonalds, on Bourges Boulevard, in Peterborough, at about 4am on 22 August last year.
Zukovskis told the victim he owed him £20 after the teenager had allegedly sold Zukovskis fake Apple earphones a few weeks earlier.
He snatched the victim’s phone from his hand before making him in reset the device.
Then, on 28 September, the victim was talking to three friends in Viersen Platz when Zukovskis once again approached with two accomplices.
When the victim tried to walk away, Zukovskis followed him and demanded money or his phone. The teenager attempted to run but Zukovskis stopped him by punching him and throwing him to the ground.
The trio then beat up the victim before Zukovskis stole his phone from his pocket.
The victim’s 21-year-old friend attempted to help but was repeatedly kicked and assaulted and also had his phone stolen.
Zukovskis, of Tirrington, Bretton, Peterborough, was arrested and later pleaded guilty to robbery, theft and handling stolen goods. He was sentenced to three years in prison at a Youth Offenders Institute at Peterborough Crown Court on Tuesday (22 December).
DC Andrew Donaldson said: “Zukovskis targeted the victims following a petty dispute about the sale of some earphones.
“His brazen and violent behaviour was completely unacceptable and I hope the victims feel some measure of comfort following the sentencing.”