I am working on a custom solution that requires additional fee items to be added to a checkout. The fee amount depends on the customer's address/region and cart items.
I am using draft orders for this purpose as custom line items can be added to a draft order.
The flow of this solution would be to first ask customers for the shipping address on the cart page through a custom form, create a draft order through the Shopify Admin API with the cart items and address, calculate the price of the custom line items according to the address and cart items, add them to the draft order and then redirect the customer to the draft order's invoice url, which will take the customer to the Shopify checkout from where they can complete the rest of the checkout process.
But if the customer changes their address on the Shipping information page, the custom line items' price can become incorrect or irrelevant giving customers an incorrect subtotal.
So, I would like to know if there is a way to prevent customers from changing their shipping address from the Shipping information page on checkout, without Shopify Plus.
Any solution on how to accomplish this will be appreciated.
Please feel free to ask any further questions if required.