A gatekeeper is the person you see first, first person to pick up the phone and who needs to give you permission to see the decision maker.
So to get past them on a phone call, you need to tell them who you are, where you are calling from and why you need to speak to them
Gatekeepers are always willing to help if you respect their position and give them a good reason.
Forget saying this is a business call, it’s personal.
You give them what they want and you will get what you want.