I'm in Ireland, so the time scale might be different as might the system, but I didn't get a call at all. They sent the results to my GP and I had to make an appointment with my GP to receive them.

It's also pretty unlikely you'll get bad news from the ultrasound. It can't diagnose cancer. The odds are very high that the next step will be to arrange a biopsy. That doesn't mean there is bad news or that they are worried. Most thyroid nodules have to be biopsied. I believe there are some where the ultrasound shows features so low-risk that a biopsy is not needed, but that is a pretty small number, from what I remember of the reading I did when I had an ultrasound. So it's either good news - the nodule is really low risk and everything is fine - or neutral news - we can't rule cancer out so a biopsy is needed. Only about 5% or 10% of those biopsied are cancerous, so going for biopsy does not mean cancer is likely or that there are feature of concern.

I got my results a week after the ultrasound, I think and the biopsy was...maybe 2-4 weeks later.

The worst you are likely to be told is "we will send you for a referral for a biopsy" and I'd say even that is unlikely over the phone. Most likely, it would be something like "your GP has the results of your ultrasound. Schedule an appointment to discuss them with him/her."

They would have to do a biopsy before deciding on a thyroidectomy.