False ANSWER

If you are using GREY routes (not legal) be ready to experience false Answer.

That means that i some way between caller and callee some "grey" provider answers the call but still plays ringing sounds to fake the call.

The call will be marked as ANSWERED but in reality nobody will answer.

To avoid this - talk with your provider or use "white" routes.

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This is very often happens with Betamax company group providers: http://backsla.sh/betamax