Hi @yangjp2333 ! Thanks for sharing your flow and context of what you want to achieve.
Since the purpose of the upsell is to add another product to the original order, there isn’t a way to natively have the selection overwrite the option chosen in the checkout. Nevertheless we’ll keep this in mind for future improvements.
For now, the easiest way to tackle this would be by allow customers to choose the option from the landing page:
1. Show the options in the landing page
- Monthly subscription
- Quarterly subscription
See this post here: How to Pre-Select Products in Checkout Directly from Your Landing Page
2. Create 2 checkout pages
- 1 checkout page Monthly subscription
- 1 checkout page with Quarterly subscription
3. Link the buttons in the landing page with the corresponding checkout URL
Let me know if you have any further questions,
Belén @Funnelish