In the US, registering your number with the 'Do Not Call' list will only help you with ~ 5% to 10% of the unwanted calls.  The remaining 90% to 95% are from 2 other sources; 1) illegal scams / fraudulent entities (mostly operating outside the US), or 2) government's sponsored entities not covered by the Do-Not-Call-List such as charities, politicians, etc.  For these unwanted calls, we recommend a call blocker.

On the other hand, call blocking services offered by phone services in the US are too expensive (usually require a recurrent monthly fee ranging from $6 up to $20 per month). They are also very limited, usually blocking less than 100 unwanted phone numbers.

A call blocker device is a lot more cost effective (one-time purchase ranging from $40 to $100), and you can help you block up to 1,500 unwanted phone numbers.