Hide shipping method if free shipping is enabled

Hi,

I have created two different shipping methods with your plugin:

1) One method based on weight (0-5 Kg–>3€ and 5-10 Κg–>5 €)
2) One second method based on price (Free shipping for orders over 30 €)

The methods work correctly but while being on the cart page, if I have added products over 30 €, Ι see both methods and not only free shipping as desired.

How can I hide the 1st method in case that 2nd method takes place?

Thank you in advance.