You can set up the voicemail system on your iPhone by opening the phone application on your device. When the app opens, tap on the Voicemail tab and then tap on the Set Up Now option. You will then require to insert a password to protect your AT&T wireless visual voicemails. Please enter the password again to confirm it, and tap on done once you have secured a password. Select Custom or default next; selecting Custom will allow you to record a new greeting, and default will keep the general greeting at your voicemail. Once you are done, tap Save.