Atletico Madrid striker Costa has elected to play at international level for Spain, where he has played club football since 2007, rather than his native Brazil.
Costa was rewarded for a stellar 2013-14 season with Atletico - which saw him score 36 goals in all competitions and help the club to their first Liga title since 1996 - with a place in Vicente del Bosque's 23-man squad for the World Cup.
The 25-year-old's decision to declare for his adopted homeland caused plenty of controversy, and Scolari appeared to stoke the fire earlier in the week by saying he had told Costa he would be included in Brazil's World Cup squad before he pledged allegiance to Spain.
However, Costa has refuted the Brazil boss' comments, while insisting he will give his all for Spain as they seek to defend the trophy they won for the first time in South Africa four years ago.
"Scolari never called me by telephone," said the forward, who played in two friendlies for Brazil in March 2013.
"The only coach that I spoke with was Del Bosque, who showed interest in me, invited me for a meal and made me realise that I was in his plans.
"I am Brazilian and that is not going to change, but I want to win the World Cup with Spain."
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