From the first time you make an order, your payment shall come off the day you make your order and for subsequent delivery frequency it will also be on that same day.

eg: for example if your delivery day is a Tuesday, but you ordered and paid for your veg on a Thursday your payment will come of every Thursday either weekly, fortnightly etc.

So if you do need to make any changes you must login to your account details before that payment day, or the original order shall be dispatched and payment taken.