change from https to http (on wordpress.com)

I have an wordpress.com blog and recently changed to my new self-hosted website (also wordpress). I wanted to tell Google Webmaster Tools to change the adress from maremmageheimtipp.wordpress.com to maremmageheimtipp.com. Webmaster Tools told me that the 301-redirects didn’t work, so I was not able to get my new adress confirmed. Later I realized that Google first redirects from https://maremmageheimtipp.wordpress.com to https://maremmageheimtipp.wordpress.com before finally redirecting to my new domain. I think that’s why Webmaster Tools tell me my old site does not redirect to the new one. What I want to do is change the canonical url from https://… to https://… to avoid the first (unnecessary) redirect. Unfortunately it’s not possible to make these changes in Webmaster Tools … so how can I make them on my (old) wordpress-website?

Thanks so much!