Currently only the taste of individual products can be changed (e.g. "Whey Protein Raspberry" to "Whey Protein Chocolate"). You can set this yourself in your account under "My subscriptions".
However, if you would like to change the number of products or individual flavours in a package (e.g. "muscle building package"), please contact us with your subscription ID via our contact form "Subscription/Bonus Program" > "Subscription". We will then terminate the subscription for you so that you can place a new one with the desired products.