You can cancel your Diggz Premium at any time. Once you cancel, your membership will not renew at the end of your current subscription period and you will not incur any further charges. Also, when you cancel, your Diggz membership will still be valid until the end of the current subscription period and you'll continue to enjoy the perks you paid for. So you can cancel at the beginning of the membership or the last day, you'll still get what you paid for.
To cancel your membership, simply scroll down to the bottom of the 'edit profile' page and click on 'Cancel my Diggz Premium subscription'. It's that simple.