"0800 numbers used to contact patients"

I have been waiting for over a year to get a second scan to check the progress of a tumour. I was supposed to get a scan 3 months after my initial consultation in Oct 2019. I got a letter a few weeks ago saying I would get a phone consultation a couple of days ago at 10. 50 or sometime in the morning or afternoon of that day. I waited until 4pm and called the local number. They said they used an 0800 number to contact patients and to put it in my contacts on my phone. This I did and discovered that the urologist had contacted me at 11. 50 that day and that the call, like all other 0800 numbers on my phone, had been rejected. Not only that but I had been contacted in Feb and March of this year on the 0800 number and my phone had rejected both calls. I wasn't contacted by letter in Feb or March and would never have known about the calls had I not added this 0800 number to my contacts yesterday. I have been worried about the progress of the tumour but assumed Covid had delayed getting a scan not that an 0800 number had been used to call me.   I am now waiting for a scan, hoping it hasn't grown too much. Why on earth use an 0800 number?