Engage, don't evade the gatekeeper
Don’t try to sneak past the gatekeeper, but actively engage with them. Don’t get too personal and don’t pry, but you can gently probe.
Source: Sales consultant Andy Dickens
If you can't get through to the decision-maker, engage the gatekeeper so that they have a positive and friendly attitude towards you when you call again.
You're unlikely to become best friends, but building a relationship and a rapport with them will help them want to help you.