Log into freephoneline.ca and then click on the 'Account Settings' link at the top (
https://www.freephoneline.ca/updateAccountDetails) Along side the 'current password' box you will see a delete link. Deleting your account will also delete any worldline credits, unlock keys, or porting you have done on the account.
This should allow you to start again.
Yes the FPL desktop account is just a phone on your computer using your speakers and mic. You can later buy the unlock key which will allow you to use an ATA and then a normal phone.
If you want to be able to text and make call on your cell phone, then head over to Fongo.com and sign up there.