LookoutforChris's dashboard

With every SMS sent to my iPhone Sandy's phone number goes up so it's hard to keep track of her. The last reminder I got was from 1 (010) 100-018, then next will be 019. I have an iPhone and I'd like Sandy to have a fixed mobile number so I can add her as a contact and have the reminders organized under her name in the SMS app (just like all my text messages from friends, etc.). Why does the number change with each SMS?