There are billions of unwanted robocalls and robotexting each year. To help block these calls, register with the FTC National Do Not Call Registry at DoNotCall.gov. Legitimate telemarketing companies should reference the registry to avoid numbers that are on the opt-out list.
Other tips to avoid unwanted robocalls are:
Do not answer calls from unknown numbers
Hang up immediately if a robocall is answered
Do not respond to any questions, even if the answer is a simple "yes" or "no"
Never provide personal information