Making and receiving telephone calls is one of the hardest skills in English. As we can’t see the person we’re speaking to, we can’t use the usual non-linguistic signs (gestures, facial expressions etc) to help us understand the other person.
However, we often use standard phrases during a phone call, and learning these will help you not only understand what the other person is saying, but also direct the telephone conversation so that you can communicate your message successfully and concisely.