Worldwide calls forwarded to UK/USA/AU

Hi guys,

We are hoping to build up a business that would provide instant interpreting services so we would have customers in most countries around the world and have offices in the UK/USA and Australia.

We’d need to be able to control how much our customers would need to pay for purely the phonecall alone (and make it cheap!).
From my research it seems like we could buy DID numbers in each country ? This would be a lot of people calling and a lot of one time only users.

Does anyone have any ideas and suggestions for us to get this to work?

Thanks for any help!
Marie