Phone customers with these services can turn on automatic call rejection with a two digit code preceded by star. They can turn it off just as easily. There are other two-digit codes to block or unblock Caller ID display for an individual call. Telemarketing is a way of life, but you have some safeguards. Make a record of the date, time, identity and your request.
Many states have laws that require such requests be honored.
Two things the telephone con artist will try to learn is your bank card or checking account number. Under no circumstances should you ever reveal these numbers. The caller may say they need the information to ship a prize or process the fee for the credit card. It's processed like a check but does not require your signature. You don't learn the bank paid it until you get your bank statement.