I said hello and also got no reply. I like to know who is trying to contact me before I block them. Most likely scammers. If you can identify this caller please post. Thanks!

called back and got voicemail immediately telling me if I don't want to know about special offer and to be put on do not call list to press 1.  

i didn't pick up.  Stop calling me, please!

Consider getting a call blocking device or phone.. You can google them and many are around $40.00 or so. If its a cell phone, some already have call blocking, if not, there are free apps on the web that will work for some. You can google this. If you have a smart phone, there is a free app called call control. Iphones appear to have apps also. Another one is called Mr. Number.

Report your callers here, not just to the DNC alone:

https://www.ftccomplaintassistant.gov/#&panel1-1
https://esupport.fcc.gov/ccmsforms/form1088.action
https://complaints.donotcall.gov/complaint/complaintcheck.aspx?panel=2

For text messages: forwarding any text message spam you get to the short code  “7726,” which spells “spam” on most phones, to alert your network operator to the abuse.

By State DNC lists:
http://800notes.com/res/DoNotCall.aspx

FCC Abandoned Calls Complaint form:
http://www.fcc.gov/cgb/consumerfacts/1088D-R.pdf
email:  fccinfo@fcc.gov

To file complaints on Foreign company's:
eConsumer.gov: Report Your Complaint
E-mail: econsumerwb@ftc.gov