On exiting the car park the machine did not recognise my prepaid ticket. I phoned helpline which was answered after a few minutes. I explained situation, registration number etc, I was told to wait where I was as somebody was coming up to see me. A person arrived in a van and said they had no record of my booking on the system and demanded my reference number. I was able to provide this on my mobile phone, they then asked was I sure I had booked parking at Aberdeen, again I was able to demonstrate that the booking on my phone did state Aberdeen. Eventually they opened barrier and let me out, the episode lasted about 15 to 20 minutes. Not impressed with the technology or the attitude when I was able to present the evidence