Yes! A good telephone manner just means you can talk clearly and politely and you already have IT skills if you are on Mumsnet. If in dobt, just say you are a quick leaner and are willing to be shown how to do things. If they get a better qualified candidate, you may not get the job, but it is worth a go surely?
No no no. I used to do this sort of job during the holidays when I was a student. If they want recent experience, I expect they mean experience using an exchange. Well, I used several and they were all different. Just say, no I haven't used that sort before but if you show me how it works, I learn very quickly. How hard can it be anyway? Obviously, speak nicely when you ring up so they know your voice is clear and prefessional sounding.