Errr, no they don't. Yes, they must be disable-able. It does not require the phone maintain the same functionality, etc. For example, Verizon makes visual voic

Errr, no they don't. Yes, they must be disable-able. It does not require the phone maintain the same functionality, etc. For example, Verizon makes visual voicemail only available on the verizon store. You can disable it, you can remove it. That won't get you the functionality!