Why am I still getting unwanted calls after I signed up for the Do Not Call Registry?

Q & A Main Article 2

Signing up for the Do Not Call Registry should stop calls from most legitimate telemarketers and businesses. However, some calls are exempt (charities, religious groups, political campaigns, surveys, customer service calls, etc.), and it’s also possible for scammers to make these calls using pre-recorded messages (robocalls) and spoofing their phone numbers.