Android Voicemail app

The app needs to do the following : 1. Logs into the users voicemail account (hopefully it can leverage the password that most people have saved in their phone so the user doesn't have to enter this password again. 2. Gets a copy or records a copy of the users current voicemail message. 3. Prepends a prerecorded humorous message in front of their voicemail and then uploads the new message to the users voice mail account. 4. There are many many phone providers in the use so the number prompts to get into voicemail to get the message and then uploade the edited message will likely depend on the phone provider Example User John downloads our app either for free or paid User John allows the app and then clicks GO The app logs into User Johns voicemail account and gets a copy of the recording that User John is currently using... something like: "Hi, its John, and I'm not home right now so please leave a message at the tone" Once the app has the recording of User Johns vm message we prepend our humorous one so it now sounds like this: "HEY ITS PIZZA HUT, WHAT kind of pizza do you want BOZO! HA HA HA HA... Hi, its John, and I'm not home right now so please leave a message at the tone" Now the app needs to login to User John's voicemail and upload the new combined message. I also want advice on if we should: 1. go Free version with Paid version or straight to Paid version and 2. if there is any way we can build a list of who downloads our app so we can market to them, is it possible? Queries : my question is if the user makes a new voicemail with this app how will you get it to play on voicemail? is there an api or way to easily upload this new file to voicemail?