I was faced with the same issue (occurring over many years). Within the past few months, I downloaded TrueCaller for my Android phone (as my phone based "block" list was full at 100). Now when they call, I block the number with the app and they never get through again with that number. There's also a community that reports these types of calls and TrueCaller apparently uses that database to alert you to other scams/spams from there.
I have found it invaluable. I do not have any vested interest in TrueCaller but just passing along some information that helped me. Best of all, it's free.
These U S Pharmacy calls relentlessly from India. Requesting for them to stop calling or stating no one in the home takes pharmaceutical meds does nothing but increase the frequentness. It may not solve anything but it sure felt good calling the India Embassy in Washington D.C. and asked one of the diplomatic representatives to please do something to stop the relentless calls originating from India and the company U.S. Pharmacy. To demonstrate the endless harassment I call the Embassy daily for a couple days. I don't like being a pest but surely this gets the point across.
Incoming call from middle eastern male, he is following up on the medication that was shipped to me... (i dont take meds) i told him he had the wrong number, he hung up. called back within 48 hours with the same shtick. i have had this conversation with these a-holes about 20 times in the past 2 months