If a supporter asks you to cancel their pledge, there are two options as long as there is more than 24 hours remaining on your project.
Find the name of the person and the pledge then press the 'Cancel and refund' button next to that pledge...
2. They can cancel the pledge themselves.
When they are logged into Crowdfunder, navigate to the 'My Pledges' section of the user drop down menu in the top right hand corner...
Then click on the plus sign next to the pledge they want to cancel
Then click the cancel pledge button
There must be over 24 hours remaining on the project in order to cancel a pledge from your Crowdfunder account.