Who does this seem to be coming from??? AC, Microsoft, someone else, not sure who yet? Have you stayed up on your updates and your annual renewals I presume? If so it could either be a clerical error back at the AC home office that is easy to fix or someone who is pretending to be AC some how to try and get your credit card info I might guess?
You are right in be safe and going slowly. I'd be curious to see what AC does say to you. I hope someone hasn't gotten all of our info some how from here or elsewhere. Have you gone to and regisitered at any other places like EMR updates and the like who might also know who your EMR vendor is? Just a thought... Good luck and keep us all in the loop as you figure it out....