Changing between multiple Teams Free accounts within the app or browser
Open this link in your browser using the InPrivate mode:
Sign now in with exactly the same credentials as you have used with Skype. If you have used a legacy Skype Name as the Login ID, use the same Login ID for Teams.
Note however the forthcoming changes to the old Skype history which will affect users who transferred to Teams later than December 1 2025.
Please, read the explanation provided in this support article under the heading: "Updates to Skype chat and call history in Teams Free"