Forced to enter additional digits after dialing an international call

rzgtrk@gmail.com

    I have the 15$ Stateside features, and i'm calling always to international numbers, some of them, connects immediately, and start charging me, and broadcast me a voice message: If you want to continue this call, press 37 (random digits), after pressing the 2 digits it starts ringing, all this procedure while charging me, and this makes me extra charges on international calls, how to deactivate this? Or to make this message free of charge at least..

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