Refunds are only given where legally required: https://help.dropbox.com/plans/refund
You can contact support via www.dropbox.com/support for help if needed. If you do not get the option to do so you are logged in to a free account which you've not paid to upgrade. Therefore you need to log on to the RIGHT account and contact that way. You can look up credit cards using this tool.
If that all doesn't work log out of here and use an incognito window to go to www.dropbox.com/support and log a ticket about issues logging in. However, you will ONLY see that option if totally logged out.
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