I was in Colombia for 10 days recently and couldn't access my voicemail:
- 443 simply didn't work;
- I hadn't set up PIN access to my voicemail and would be a bit reluctant to incur the charges that would involve.
That got me thinking: why not make voicemails available as sound files online? You go online (usually free in your hotel using wifi), log into your account, click on the voicemail message link and listen to it through your speakers or headphone. That way, it's free and you still have voicemail access in far-flung places where 443 doesn't work.