What are the two speakers talking about?

W: Hello, this is Jenny Hart speaking.
M: Oh, hello, Jenny. Simon here. Simon Wills.
W: Oh, Simon. How nice to hear you! Are you ringing about the party? You did get the invitation, didn’ t you?
M: Yes, thanks, I did. That’ s just it, I’m afraid. You see, I’m already tired up that evening.
W: Oh, Really? That’ s a pity.
M: Yes. You see, some friends of mine from Scotland are coming down. I haven’t seen them for ages and I managed to get some tickets for a concert, and I promised to take them out for dinner afterwards. I can’ t get out of it, unfortunately. I wish I could.
W: Oh, what a shame! We were looking forward to seeing you. Still if you can drop in later with your friends, we’ d love to see you.
M: Thanks. Well, I’ 11 certainly try, but I don’t think there’ s much chance. Actually, I’ ve sent e-mail to say I can’ t come.
W: Oh,have you? That’ s very kind. Thanks. Well,keep in touch,Simon.
M: I will. Bye.