Hey guys,
A friend of mine has asked about setting up a proper phone system for their business. Currently they have a single Vodafone fixed line. They are an immigration consulting company with clientele mainly from Argentina, Brazil, Chile and Mexico. They have virtually no computing infrastructure so looking at a solution with minimal hardware. Initially I thought of a hosted VOIP solution such as one which kiwivoip have but we discussed the possibilities of having DDIs in the 4 above countries so their clients don't have to pay huge amounts to call them.

Currently they are in one location but will be getting a small office in another location so will have 2 locations.

So ATM I'm thinking of a small VPS running Trixbox/Switchvox with OpenVFX to start off with. Then connect into it via the net using Yealink IP phones. After that is setup and working we can look at adding some other VOIP provider who can provide multiple DDIs over the one trunk.

Does this sound like a good plan? My only concern is really with security running SIP over the internet and getting hacked etc. Any suggestions on a good trunk provider who can provide multiple local DDIs under the same account/trunk?