As Matha said, billing on forwarded LD would be billedl like direccted dialed LD. ATT in this case.
HOWEVER, most local carriers (major exception is Verizon) do NOT permit you to program the system to forward to intl. numbers. SBC does not.
I have had to use
www.kall8.com to forwardd calls overseas. Forward my calls to the Kall8 number that then forwards to overseas number.
I am hoping that YackieMobile, being discussed in another thread here, will solve my problem. They give you a "local" number keyed to your intl. SIM. They seem to be a new start up and they won't be sending out SIMS for about a week. No one here has tried them, yet.
...mike
Make use of T-M's UMA/wifi free calling from any place in the world with access to wifi. I use an LG G6, wife an S7)
A/o Oct 20, 2013 no need for intl prepaid as T-Mobile U.S. includes voice roaming at 20¢/min (in and out)., unlimited text (in and out), and unlimited data in 140+ countries.
My Plan -[6 lines] U.S. T-Mobile unlimited minutes (incoming and outgoing), unlimited text, fast data on each line. that $145/mo. total! . (In U.S. no surcharge for calling a cell.) If a line exceeds 2G of data in a month, pay $10 more for that line. [That only happens a couple times/year.