Elisa Netti kotiin S

You can do it in Omaelisa :) https://verkkoasiointi.elisa.fi/

No i can’t, I try before I ask here, and there no one answer me 

When you select your product from the list in omaelisa, click “Sopimus ja omistaja” :

From there you can select “Päätä sopimus” :

Of if you use Oma Elisa in English, the same:

Products and orders → Kiinteä Laajakaista → Contract details and owner → Terminate the agreement