What should I do if I'm not sure of the right ruling during a medal round?

In stroke play you can play two balls under Rule 20.1c(3), without penalty:

• Decide to do it after the doubtful situation arises and before you make another stroke.
• Tell your marker or another player which ball you want to count. If you don't choose, the ball you played first counts.
• Complete the hole with both balls.
• Report the facts to the Committee before you return your scorecard, even if you scored the same with both balls. If you don't, you are disqualified.

Other points (Rule 20.1):

• If no referee or Committee member is available in a reasonable time, you must decide what to do and play on.
• Players can help each other with the Rules, but you can't settle a Rules issue by agreement. Any such agreement doesn't bind the Committee.
• If you believe another player has breached a Rule and isn't owning up to it, tell them, their marker or the Committee before they return their card. If you don't, the Committee may disqualify you for serious misconduct.

In match play there's no two-ball option. If no referee is available, tell your opponent you'll be asking for a ruling later. You must make that request in time, or the result of the hole stands.