Missed call from Atos?

I am hoping someone can help? I missed a call earlier today and when i've checked the number it is from atos. I sent my esa form off about 3 weeks ago so i guess it's the dreaded call to invite me for a medical?
I stated on the form that i don't answer the phone unless i know who is calling due to anxiety problems,etc. What would happen if i did not answer the phone? Would they send a letter?
Also roughly how long after "the call" are you asked to attend?
Would they ring to say i've been placed in a group without a medical?
Sorry for all these questions but i'm going to have a sleepless night tonight with worry, i'm really scared now of what's to come?

If they cant get you on the phone they will send a letter with an appointment. I think they have to give at least seven days notice.

Hi titchy123
When Atos have phoned me it has been to attend a medical. I miissed the call last time they phoned and 2 days later i received a letter to attend a medical. On both medicals i have had about 3 weeks notice. I would be as sure as i can be that if ATOS have phoned you it is to attend a medical.
Mike