To cancel your credit card subscription to skugrid, please log into your skugrid account, click on Subscriptions.  Then click on the Unsubscribe link that you see in the table of your recurring subscriptions.  Follow the screen prompts to cancel your recurring payments.

If you no longer intend on using Sku Grid, you can then choose to either go to Settings --> General and set Vacation Mode to Yes.  That way skugrid will not check or reprice your items or you can Purge them all out of skugrid. If you do not do one of these options your items will continue to be repriced until credits are gone. 

Additional Videos: 
Setting Sku Grid on Vacation Mode to Stop Credit Usage -
How to Purge Items Out of Your Sku Grid Account -