You can Complete the order manually from the Admin. That way you do not have to pay for your pixels.
Once you complete the order, you can publish your pixels.
Additionally, you may set an advertiser's account to privileged mode. Here's how:
1. List Advertisers
2. Click on the Advertiser's username
3. Select the "Privileged User" radio button in the account status form.
A "Privileged User" will be able to make orders for free, without any other limits.