Although the quality of iPhone 4 CDMA calls has improved, they may sometimes not be heard well, depending on the service coverage and where you are. If you are at home, or in a place with Wi-Fi, you have bad reception and you are forced to make a call, the best thing you can do is make an iPhone to iPhone call with FaceTime Audio .
How to improve the quality of calls on iPhone
This is still an unknown feature for many Apple phone users, despite being one of the hooks used by Apple in the presentation of iOS 7. There are two ways to use FaceTime Audio: enter your phone book or app. Open the phone app and click on the Recent button at the bottom of the screen. Then, click on the information icon to the left of the contact you want to talk to. In the middle of the screen, you will see the FaceTime section and you will have the option to choose the video or audio icon. Choose the phone icon to start an audio call through FaceTime Audio.
Another way is to enter the FaceTime app and click on the contact button in the bottom center. Something simple, but that will definitely improve the quality of the audio . It should be noted that the other person requires an iPhone, iPad, ipod Touch or Mac to make this work.