Can you please let us know what country and region you are calling from? Also, can you clarify what you mean when you write "800-709-7779 is empty"?
To make international calls, first dial 00, the international calling access code used in the country. Then dial the country code for the country you need to reach (1 for the U.S.), followed by 800-709-7779.
Besides that, you can also try to make the phone call using VoIP and see if that works.
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