"Arriva cancelled and my mum missed her appointment"

I am absolutely disgusted with Arriva. My mum was booked in to go to the Great Western Hospital in Swindon, Wiltshire at 11. 55am. At 11am, someone from Arriva contacted us to ask what assistance my mum needed. We told Arriva that my mum needed a wheelchair and someone was going to get back to us but it wasn't until we contacted the department at the hospital that we realised that Arriva was running an hour and a half late. Now this has happened, my mum missed her appointment and had to wait another week. During the time between the missed appointment and the rebooking, my mum was admitted to hospital due to an underlying infection (sepsis). Had she not missed the appointment that she had booked this could have been picked up and dealt with. I would also like to point out that my mum has secondary breast cancer and is terminally ill. These appointments are vital for my mum's wellbeing. This is also not the first time this has happened.