uber drivers

Good morning. i am very upset with uber. I have being using for quite some time. this pass 2 days have been a nightmare. i requested a ride for both days. both days we paid the driver cash but the driver said we didnt pay him. we did pay him the full price. no1 responses to emails calls etc. very disappointed and uber is charging me for the trips which I paid for but the drivers are taking the money and saying we didnt pay.