And why wouldn't it be expensive?! You're asking for quite a sophisticated facility.
This has been done here regularly; try a search. My own solution is to keep Compuserve going at about £7 a month. I pay for my phone calls abroad too. My US friend uses his AOL account for which he pays at home but the benefit is that he can make toll-free calls whilst in Europe.
How far are you going? Compuserve wouldn't work in NZ because the local licencing was different to up here so I needed a different script file. Do a lot of homework before you go; I didn't but will next time.
This is all I could find in the last six months; looks like you'll have to go back further.