Medco is a legitimate pharmacy (part of Express Scripts) and supplies maintenance medications to employees of large companies. But, as stated above, this is NOT one of their legitimate phone numbers.
I got no Voice message, and the very same number called my land-line about 20 mins earlier. I answered the first one (unfortunately) and it appeared to be someone from an ad service, trying to sell my former business some advertising space in a phone book or online. I closed that web biz down almost 5 yrs ago!
Needless to say, I requested they remove the number.
The woman at the other end said it would be done.

I've found, with a lot of these unwanted callers, that it is best to answer and tell them the person they want is NOT at that number, or hasn't owned the number in years, or died (Ha!). Even if that person is you. That usually stops them from calling anymore....faster than yelling, reporting them to the DNC registry, or anything else. Though I have had fun calling them back a dozen times just to piss 'em off.

Next, I plug the number that called into my handy little call-blocker on my phone and no more problems!
The phone doesn't even ring IF they try to call back again.

Yes, most call block programs only allow about 20-50 numbers to be programmed in.
So about once every 3 - 6 months or so, I come to this site, re-check all the numbers to see how old the last post is. If it's been more than 4-12 months since anyone has posted about a number, I delete it from the blocked list because it's obviously been dumped by the company using it - which makes space for a new phone number to be added! Works like a charm!

Especially since I don't even have to hear the phone ring on blocked calls. It goes straight to Vmail on my land line. On my cellphone, I have an app installed that sends blocked calls right to dead air. Mwahahahahaaa!

I highly recommend the satisfaction gained from using a blocking system. :)