This is not a iOS 7 problem because I've had this issue for all of the last several bigger iOS updates for a couple of years and its not a phone specific since I've replaced iPhones and it still happens. I have issues with deleting visual voicemails from the deleted folder. Most of the time after you delete the voicemail and you go into the "Deleted Messages" folder, it takes 10+ minutes or so for the "Clear All" to become active. I've tried restarting the phone but the "clear all" is still not active to delete. Ideas or comments?