Hi @bingyan1 can you provide a little more information? Fido charges a month in advance (so in your last invoice you would have paid for the coming month). So I'm expecting that this invoice is explaining to you that we are refunding part of the amount you paid in advance. You would also have to pay for any usage you did (eg. long distance) that isn't included in your plan. However without more details it's not possible to explain what exactly you are being charged for. Suggest for you to contact us so we can review your bill in detail with you, will be easier.
We're sad to hear you cancelled
If you cancelled on the 17th, and your bill cycle is the 23rd of each month, then the final invoice should be the December 23rd invoice and it should refund the period of December 18th - December 23rd.
Is that the case? I suggest downloading the PDF version of the invoice to see all charges and credits
Let us know!