"Unclear explanation around access to scan"

I didn't really want to make further comments, as I understand the pressure that NHS is facing all the time, but it is a most unsatisfactory rearrangement that has been provided to me for this appointment.

I was offered another appointment for this month with less than a week's notice, on a day that I'm going to be away again in another city! Unfortunately I would be unable to attend the appointment exactly on that day, therefore had to turn it down again! The receptionist told me that it was not known when the next appointment would be offered to me, as I turned down the appointment twice, the February one and now a March one, and that there was no alternative because this was a special type of scan.

Is it my fault for not being able to take the appointment? Am I supposed to sit and do nothing but wait for the appointment that might or might not happen for six months so that I could take the appointment in less than a week when it suddenly appears?

Why is it not possible to schedule the appointment further in advance if it is said that this is a special type of scan that only a few specialists can operate? I would imagine that it would be even more possible and logical to schedule appointments well in advance because the hospital already knows that there will be months of waiting time and knows where and when exactly resources will be.

After months of waiting, then giving me less than one week notice in advance for the appointment without alternative options, is unacceptable. It happened to me in February and now again in March. It also looks to me that the appointments are only available at the end of each month, which is beyond my comprehension. I am considering taking this to my MSP.