Why do I keep getting phone calls saying there has been a breach in my account. How can I know it’s not a hacker

It is a scam. Hang up or don't answer. Apple does not make unsolicited phone calls. Also see: Avoid phishing emails, fake 'virus' alerts, phony support calls, and other scams - Apple Support

It is a hacker/scam. There have been multiple posts about this recently. Apple will never call you unless you called them and asked for a call back.