VoIP or IPCL question reg connecting off

We are here in the US and we have a setup in India for development of our product. We want to provide support for our clients from India. We dont want to setup any call center but we just want one or two lines where our client in US or anywhere can dial an USA number (toll free or otherwise) and talk to our ppl in India. Similarly our developers in India should be able to dial any US number from there.

I have been informed that VoIP may be a solution but there are concerns about the Quality of Service and the leased line option wont work for us as we just want one or two lines and so want to keep our initial investment in check.

What would be my options? Are there any end-to-end providers?
Can someone provide me a proposal/ quote?
Please send an email to unmesh@myway.com

Thanks in advance.
Unmesh