Using PC fax on VoIP

Hi,

I hava VoIP connection from Vonage. I try to send fax through PC, as I donot have any fax machine. But here I face problems while I am sending the fax. I tried to reduce the data port speed on the modem of the PC to even 1200bps, disabled EC on data protocol setting, disabled compression, no flow control on the modem setting but still fax call is being dropped. I donot why? I checked the internet speed which way above 3Mbps download and 600kbps upload. I use DSL Internet Service.

Please help me in finding any solution.

Thanks