From A Weak to Confident Communicator - 30 Day Challenge
Everyone's time is precious. When you walk up to another person to ask for help or when you call somebody, you are consuming somebody else's time. Therefore, you must ask for permission first.
You do not have to ask in a formal fashion. Just a simple question to check if the person is free works well. When you ask such a question, people feel respected which in turn makes you likable. The other person is more likely to help you too.
Today, when you approach someone with a question or a query, ask a question first which is something on the lines of, "Is this a good time to talk? I will take about 5 minutes." You do not have to use the exact words. Feel free to use your version to check if the person is free.