I'm also having this problem. My carrier is CTT Portugal, and when I add the tracking code it automatically thinks it is "La Post" and adds the incorrect tracking URL. This is so time-consuming for me...
I changed the email template to ignore the wrong URLs and send always the correct tracking URL, but on the order status page, the URL is incorrect if I don't manually add an URL.
Even using "NONE" does not work as Shopify wrongly assigns "La post" all the time.
Please add "CTT Portugal" or at least give me the option to add my own. I'm even considering to move to Jumpseller due to the lack of this and another integration.