In this particular sentence, the轉折 ("快點我要給我打電話我要睡覺了") is significant because it changes the direction of the conversation. Before this轉折, the speaker is saying "快點給我打電話," which means "Please call me quickly." However, after the轉折, the speaker is saying "我要睡覺了," which means "I need to go to bed." This change in the direction of the conversation is significant because it shows that the speaker is becoming more tired and needs to go to bed.
The sentence can be rephrased in a different way to make it more natural: "Please call me so I can hear your voice and get ready for bed. I'm very tired and need to go to bed now." This rephrasing shows that the speaker is still interested in hearing from the other person but is also提醒對方要休息了。