How many is a bunch? Without shooting the messenger, you shouldn't be using consumer-grade equipment to run a business...it's consumer grade for a reason. With that being said, and TE can correct me if I'm wrong, I think each phone call takes 64k of bandwidth, and if that's the case, you're going to fill up your T1 pretty quickly. A VPN is only going to add overhead to your traffic; I can't comment on your specific situation as to the need of a VPN. I can think of a few fixes, in no particular order:
Put a phone system across the pond
Upgrade your connection.
Upgrade switching/routing gear. Depending on the number of phones you have this may not be an issue, but you'll run into issues later with something.