'Message with sound' option on iPhone

Recently, when I add an event in my Calendar on iPhone [OS 7.0.4, iPhone 4S] I don't have an option to select 'message with sound' as an alert. The default is message only, so I keep missing appointments! Can I change the default anywhere?

I do get sound alerts for events that I have created on my iMac and synced to my iPhone.

I've had a few gliches with my Calendar on my iPhone recently (they disappeared so I had to resync from my iMac and change to iCloud syncing). Not sure if that's related.

Thanks for any help.