No the information the Coke rep gave you is wrong. If you own the machine outright you may place whatever you care to place in the machine short of alcohol. You do not need to change any graphics on the machine no more than if you have a coke sign on a door of a c-store that is from Coke and says "push" and customers buy Pepsi.
On the other hand, If you were to have a coke truck deliver to you from say north dakota then yes that would be illegal, TO THE BOTTLER DELIVERING OUTSIDE HIS AREA, not to you in any way shape or form. This is called transshipping, the coke bottler would be in a heap o' trouble from Coca-Cola hq. They would have to pay fines to the local bottler, I do not know how much it is in SD but in OK it is around $10 a case.
If what you did yesterday still looks big, you haven't done much today.