You are probably complaining about calls on a cell line but if happens to be landline, I ported one over to Twilio and actually used it to eliminate spam calls by requiring non whitelisted callers to press 2 digits to continue the call. And also saving about 7x compared to AT&T landline cost.
Connected a voip phone to it via programmable SIP.
Connected a voip phone to it via programmable SIP.