Yes, it is possible that you use your account on multiple organizations. If you are member of one organization and you want to be member of another organization, go into the settings and open “organizations”. There you can select “New organization” or a plus symbol. After that you need to fill in a registration key of the new organization, that you have received from their administration.
After that the organization is successfully added to your account and you can switch between the contacts/channels of both organizations.
You can find further information in our article (en) Merging accounts.