SERVER - Which is the best switching phone via voip?

i think the best switching phone is wholeswitch.
it could save up to 95%of your phone bills .
it's the cheapest international calls and calling card.
wholeswitch provides several services .
such as pc to phone /mobile Voip /callback/calling card/callshop/I_PBX/DID numbers/SMS services.

but i want to know the others about switching phone .
can you tell me ?
waiting for you...

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