Contacting assessment service-don't know what to say

On a waiting list with Bristol Autism Spectrum Service, have been for seven months now. I was expecting it to to be 6-7 judging from various bits of information, so feeling a bit anxious it's got to month 7 and I've still not had a letter for an appointment. They got my hopes up early October when my mum received and sent back her questionnaire, and I got a letter asking for an additional informant if possible-but I didn't have one so just sent the form back saying so-and otherwise they would send me a letter for an appointment at a later date; they were keen to get the form back, so I was kind of expecting after that that things would begin moving forwards, so that it hasn't is an additional reason I'm worried something might have gone wrong.

Think I have to call them, but I really really hate phoning people. I can do phone calls where I know the format (so I can call my bank, I can phone companies to say 'I want to cancel x') but that's about it (I even get anxious phoning my mum-I have to get her to phone me). I've been reasoning with myself for several weeks that I should call them if I don't receive a letter by x date-and pushing forwards said date each time in an effort to avoid it but now I think I definitely need to call. I don't have anybody I can get to call for me.

But I don't know what to say?? I really just want to make sure nothing's gone awry, I've not missed a letter or mistakenly been dropped from the list for some random reason. Plus I'm about to go away for the holidays and I can't help worry that what just would happen is a letter coming the day after I leave for an appointment before I come back and not knowing anything about it (sod's law and all that). But trying to come up with a script to explain that gets me into a tangle and I know I'm not going to make sense-plus I don't know what they'll ask or say or anything, not to mention the worry that something really has gone wrong. :S Any help or suggestions much appreciated.