Hey gorf!
It seems that perhaps your battery is defective. I would suggest that you go in store and see if they have another battery they could test in your phone.
If they don't have one or if the issue persists, I would suggest that you benefit from the Repair and Loaner program via the store.
The representative will be able to send your phone in for repair and lend you a phone while yours is away.
To find the nearest store from you which offers this service, please click on the following link:
http://www.fido.ca/storelocatorPlease make sure that you click on the check box next to Repair and Loaner service in order to only find the stores which offer it.
Let us know how it goes!