If you have the options of sending an email and waiting for a reply or making a 2-minute phone call, consider the efficiency of an immediate answer.
Email culture can become so normal that we do it by default. Everyone ends up being contacted by email and often the phone call is set up through an email request.
Many people are busy or have their days so organized that they don’t have space in their day to pick up an unplanned phone call.
But, many are not. Many will take just as much time to reply to your email as they will to your call, but you can get them to do it now.