There is no way at this time to change the billing due date of a reoccurring plan with WildTangent.
If the date you are currently being billed on is not acceptable to you, for whatever reason, you can cancel the current reoccurring plan, and then on the date you would prefer you can sign up for the reoccurring again.
Please note. WildTangent prices and promotions change regularly. If you are enrolled today in a plan that is no longer offered, once you cancel the reoccurring plan you will be offered current pricing. This means, your existing reoccurring plan may offer a better long-term value than a current promotion.