You can either:
A) pay for an account. It is not expensive.
or

Use
http://www.etherios.com/contactus/devicecloud and request the devices be removed from the previous account. You will be required to follow their procedure proving you are the owner the device (eg invoices from the distributor etc) and that the previous account owner (hopefully you) allows this to happen.
Please note, if you are a developer you should be using a developer account. If you are end user, after your 30 days trial, you should be paying for this service.