Atletico Madrid president Enrique Cerezo is refusing to accept Antoine Griezmann's move to Barcelona.
Cerezo claimed that an agreement had been in place between the two clubs for the player to leave for 200m in March, before the Catalans went on to activate his 120m release clause on Friday.
"If the club have made this statement it's because there's evidence," Cerezo said on RAC1.
"We have to study it and we'll demand the amount we consider to be necessary."
Griezmann's own attitude also displeased Cerezo, after spending five years at the club.
"I'm disappointed by his attitude,' Cerezo admitted. "He wanted to leave but he didn't tell us until the last minute."
But the president added: "They've made a great signing.
"We didn't want him to leave but he made his decision and we'll see if it's the right one or not."
