Does it have a case on it. If so, remove it and see if it still does it. Also, does it sound that way when she uses the speakerphone or a headset? She could try Reset Network Settings. Settings>General>reset>Reset Network Settings. Afterwards, she would need to add her wifi passcode back in. If that fails, she would need to back up everything and restore to factory settings.I purchased an iphone5c for grandaughter and since the update it sounds like a tin can and scratchy when talking to her. any suggestions plz...ty