Julie here from Shopify Support.
Thanks for sharing the link to your store. Since you mentioned that you've used an app to add the shipping calculator, it's likely that the app developers have some instructions on how to remove the calculator from your cart page.
Most of the time, instructions can be found under a "Help", "Support", or "FAQ" section within the app. There, you should be able to find some information on how to successfully remove the app; some apps require you to edit your theme's code in order to fully uninstall the app, so finding any uninstallation instructions should help you determine if this is the case.
If you're unable to locate any instructions, then I suggest contacting the app developers directly; when it comes to getting help with third-party apps, the developers themselves are the best to assist. You can find their contact information for the developer under the Support section on their app listing in the Shopify App Store.
I also managed to find this post in the Shopify Community Forums that offers some instructions on how to remove the shipping calculator from your cart page. These instructions are specific to the Prestige theme and it looks like the post has been marked with an accepted solution, so this should further guide you along.
I hope this helps! Out of interest, which app did you use to add the shipping calculator?