If the auction hasn't opened you may change the value of your bid. To do this you just need to place a new bid with your amended bid amount/quantity. This will take the place of any previous bid once it has been confirmed in the app.
Remember bids aren't able to go lower than the reserve price.
Retracting a bid
Placed a bid in error? No longer travelling? No longer want to upgrade?
Auction rules are that once a bid is placed you're committed to that auction and your bid can't be removed. While we would never break a rule, we are happy to bend them from time to time. If the auction isn't live you may still be able to remove your bid by following the steps outlined here.
Once you place a bid, you agree to pay for an upgrade up to the value of your bid if you win. To be fair to all registered users you cannot retract or cancel your bid once the auction is live.