If I am doing a REFILE on a return, do I have to pay extra? When I select "continue without upgrades it just loops me back and I can't complete the return.

You need to make sure that you have already received your notice of assessment in the mail from the CRA before you could refile. 

If you are Refiling you can do this in more than one way. The quickest and easiest would be to go to CRA My Account- If you have not registered for one yet, it would benefit  you to do so. You can also choose to do this using TurboTax- You would click on "ReFile" and do the necessary adjustment and then you will be able to file. 

Here is a TurboTax blog to help you: How to Change Your Tax Return After You’ve Filed

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