Just to inform you,the remote control in this case just added €1 extras in increments.This is exactly the same as me pressing button 4 on my meter.(valid extras are extra passengers,booking fee).
The 'scam' was that the driver had the remote hidden in the arm rest and could add extra €1s without being seen to touch the meter and alert the passenger that something was going on.
If passengers understood the charges on their receipt,and actually asked for a receipt,they would easily have seen that they were being overcharged on the extras.
There is no other way to manipulate a meter ,so if passengers asked for the receipt,they could query the padded extras on the bill.