No change drivers

Drivers arrive with no change at all, even after specifically stating that I will be paying cash.. On the app one is informed that the drivers carry limited change (it does not say they have no change).. All I needed was R20 back.. Is that above the limited change they are talking about?? My friends and I are beginning to feel that this is a trick for the drivers to pocket extra cash when customers just accept the order and leave the change for the drivers.