Building rapport is an integral part of business communication. A lack of rapport can majorly affect a conversation, so you have to make sure you make your best efforts. With a phone call, your time may be limited so you have to make sure you use the time effectively to gather enough information, which is where rapport comes into play.
Always start the call with a smile. You may think this is a silly suggestion but a smile can be heard over the phone and shows a welcoming side to you. Also show that you have an interest in the person you’re talking to, so before you get into the business side of the call, ask them about their day. This is a form of ice breaking.