Football Association chiefs have warned fans hoping to see Team GB in action ahead of the Olympic Games against buying tickets from unauthorised websites.
Some supporters have reported a United States-based website offering tickets for the double-header at Middlesbrough's Riverside Stadium on Friday, July 20 at hugely inflated prices.
An FA spokesman said: "The FA takes any form of unauthorised or illegal ticket sales very seriously, and would strongly recommend to all supporters only to buy through official channels.
"As the only warm-up match for both men's and women's Great Britain football squads prior to the Olympics, this is the last chance for fans to see the teams live and we don't want anyone to be disappointed."
Hope Powell's women's side face Sweden in a tough test of their credentials at 4pm before the men, led by Stuart Pearce and captained by Ryan Giggs, take on Brazil.