@annt100, I'm sorry that it's been 3 weeks and you haven't heard back from Mayo Clinic. If it were me, I think I would give the Mayo Clinic Rochester appointment number a call and check the status or your doctor's referral.

507-538-3270 -- 7 a.m. to 6 p.m. (Central time, Monday through Friday)

You can also try setting up an appointment online here - http://mayocl.in/1mtmR63.

Have you checked with your doctor to verify that they sent a referral to Mayo Clinic?