Phone call just 50 mins before PIP Assessment

Just wondering if anyone as had this happen recently on 5th Jan 2018 we was due to leave the house to go to my PIP Assessment the phone rang and a Receptionist at the Atos Assessment Centre said they were running quite late I asked how late one hour/2 hours? they advised the morning sessions had already ran into the afternoon. They said if I was to turn up at my appointment they could not tell me how long I would be waiting and also reminded me that my assessment itself could take at least 60 minutes. To cut a long story short. It was re-arranged for two weeks, but twice during the call the Receptionist said I could only rearrange one appointment, I had become distressed and reminded the receptionist it was they who contacted me, my partner had to take the phone why I was using my heart spray. (I have recently had a heart attack and still under further prognosis.
A friend and my sister suggested I write to both DWP and ATOS so they have a record of what took place and it was not me who was cancelling but they were unable to not only meet my appointment time but even clarify at what time or if at all I would be seen that day.