Miller Pata and Linline Matauatu dropped the first set of their quarter final against England 23-25 after squandering six set points.
The Melanesian pair trailed 14-18 in the second set but rallied to win 21-19 before clinching the decider 15-12.
Miller Pata said they never gave up.
"On the first set we worked really hard to get back up and we [were] down again on the next set, so we talked about the strategy and strong beliefs we can win the next match."
Linline Matauatu said they were made to work hard in all three sets.
"We'd say to each other we need to put the serve in and good setting and hit some balls because sometimes we play short they always pick up the ball and then we need to hit some balls to open the space."
Vanuatu will face hosts and gold medal favourites Australia in tonight's semi final and Miller Pata says they will approach the match full of confidence.
"The Aussie team are really good but we're prepared to play against them. We can beat them in their home crowd so we're well prepared to play against them."
Canada and Cyprus will square off in the other women's semi final at Coolangatta Beach after the Cypriots stunned New Zealand in straight sets.