We’re currently running a Ground Shipping Promo on purchases of 6-bottles or more. Some customers (along the Southern route) want to upgrade to 2-day, Overnight, or Cold Chain and we want to charge them the difference between ground and their preferred method.
Since that amount differs based on order size, shipping zone, and shipping method, how do we amend those orders and process specific new shipping charges on an order by order basis?
You make a good case for flat rate shipping… assuming all you need to do is simply collect more money, the only ways I can think of are:
Create an “upgrade shipping” product SKU, set it to $1. Then for each customer calculate the shipping difference, put that SKU in the cart, and override the price to the calculated amount.
Create a new set of shipping strategies, one for each upgrade. Make the $ in your tables reflect the difference for the upgrade. Create an “upgrade shipping” wine SKU that weighs 1 pound (or whatever works for your shipping strategies), set the price to $0. Put as many of those in the cart as the weight of the original shipment, and let the cart charge shipping based on the requested strategy.
Both of these completely ignore any compliance or fulfillment issues and side effects.