shipping methods, flate vs. free

hi there,
i have this problem: I have a different flat shipping rate for area. then for all the areas the shipping is free for order up of 350€.

to obtain this i created per area two different shipping methods:
1- flate rate with differnt delivery fee per area
2- free shipping with the rule of the minimum order amount of 350€

Now when i place an order with amount up of 350€, at the checkout there is not an automatic calcolation counting the delivery global rule of 350€ leving the costumer to select the option betwenn the flat rate and the free shipping one.

https://nimb.ws/Tm1R9A

what’s wrong? How to make it automatic with no way to the costumer to select it?

thankyou