If the person(s) you want to call have a voip phone you could also consider getting a free usa number from
http://www.ipkall.com and forward that number to their voip phone. Then you will only pay for a local call to the USA. Or if you have a more advanced voip router (like the Fritzbox) you can activate call through on it and make your calls that way. Maybe not the most simpel option, but it is the most flexibel one, I think
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