"Parking eye"

I am currently pregnant for the 5th time with my last 4 pregnancies ending in miscarriage. I have been classed as high risk and have been visiting the hospital nearly every week for the last 12 weeks. I was rushed to the hospital on the 14th August with suspected pre eclampsia as my blood pressure was extremely high. I purchased what I thought was 3 hours of time. I have just received a parking charge notice saying that I had been in the car park for less than 3 hours. I do not have the receipt but I always purchase more time than I believe I will be there. I attended on the 21st August knowing that I would be in around an hour but still purchased 2 hours I was only there 50 minutes. I have tried speaking to parking eye who basically won't give me the time of day. I am going through a very stressful time and do not need the extra tension of this. I think that a ticket barrier system that you pay for the exact time would be a lot better as without having to display the ticket in the windscreen you have no visibility when you get back in the car as to when the time expired. As I said this was an extremely stressful time and I'm am 99% sure that I purchased 3 hours as I only have £1 coins in my purse and am sure I paid £4 although I have no way of proving this.