Malaysian customer Alvin Teo shared messages on Facebook which showed the heated exchange between him and his driver.
Mr Teo had left his phone inside the car after using the ride-sharing service for a 14-minute drive.
But after realising he had left his phone behind, the driver demanded money to return it, according to Yahoo7.
'This phone may be very important to you, but not to me,' the driver said in a text message.
'That's not my fault but your own mistake. How much u (sic) willing to pay me to return your phone?'
The driver then suggested Mr Teo pay him rm200 ($65 AUD) to send the phone back to him overnight.
When Mr Teo didn't immediately respond, the driver said 'Do you want it or not? Don't wasting my time.'
According to Mr Teo, when the driver arrived he increased his demand and ended up being paid rm300, approximately $97, for the inconvenience.
But while some people were appalled on Mr Teo's behalf, others believed he was well within his rights to expect payment for the return of the phone.
Uber is now investigating the incident, according to Yahoo7, but their policy states that they cannot take responsibility for items left behind.