See the following from Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support
If you get an unsolicited or suspicious phone call from someone claiming to be from Apple, just hang up.
You can report fraudulent tech support calls to the Federal Trade Commission (U.S. only) at www.ftccomplaintassistant.gov or to your local law enforcement agency.
Personally I wouldn't bother. For one thing, the caller id number shown on scam and marketing calls is frequently not the number actually originating the call. The number is often spoofed. So you may not have an accurate number to report.
One option to consider is Settings > Phone > Silence Unknown Callers. See: Detect and block spam phone calls - Apple Support