IPhone AT&T Custom Voicemail

Hi erveryone - I have 3 iPhone we use with GoogleVoice and iPhone Voicemail.

We hired a company that provides custom Voicemails greetings, and they did a great job, but we havent found a way of adding a file to the iPhone, and playing over our MacBook Pro speakers into the iPhone really sounds horrible. How do get prefessional greetings into your voicemail on the iPhone or googleVoice. thanks!