Vonage Holdings has been ordered to pay $69.5 million in damages, as well as 5% of future revenues, for infringing on patents owned by Sprint Nextel.

This ruling follows a similar case earlier this year that saw Vonage guilty of infringing on three Verizon patents which saw $58 million in damages.

Sprint's claim was relating to patents for connecting internet phone calls, whereas the previous Verizon case was regarding internet phone systems.

Vonage's shares dropped dramatically as a result of the verdict, which although the company plan to appeal, has been described as the VoIP company's "death knell".