I hit redial.  Got an automated attendent with prompt for #1 to be taken off their list.  
Don't know if it will work.  Don't know why this company thinks 5+ robo calls without anyone EVER being there is going to make me want to buy whatever crap they have to sell.

These idiots give telemarketers an even worse name.

Called the number back. After a while automated system answered and thanked me for calling back.  Identified the number as a "business", but gave the option to be added to "do not call" list.  I have been getting two or more calls a day for about a month from this number or (360) 474-3948,  (253) 246-8515 -- same system.  

Never leaves a message.

I actually talked to a person from this number today.  They said that they were with a senior type service.  I very forcefully stated that I am 27 years old and not in need of senior services.  I requested that they remove my number from their list.  20 minutes later I received another call from the same number.  Again, I forcefully demanded the removal of my number from their list.  I added that if they did not, I would file a report with the FCC.

I have already filed an FCC complaint against them with my home number.  I recommend that everyone file this complaint.  I followed a link from another post.  

If we all file, maybe these annoying calls will stop!

So I've been getting calls from these guys for months.  They hang up when I pick up the phone. I too made the mistake of calling back and requesting they take me off their list.  I think others are right. If you respond, they know they've hit a real number.  Here's what you do:

Block their number (Verizon Wireless will allow you to block up to five numbers).
Every time they call, I snap a photo of it on my smart phone and keep in in my records.
Go to the FCC complaint page:

http://esupport.fcc.gov/complaints.htm?sid=&id=d1e37

You can actually attach the photographs you take proving they're calling you. I include the ones that show the incoming and my outgoing call requesting to be removed.  Do it EVERY time they call.

Received two calls, answered neither. Sure hope someone can stop this.