After accounts are moved to Teams from Skype for Business, you are still able to open Skype for Business to view chat history or connect to a Skype for Business call from someone else. When you open Skype for Business, you will need to go to the start menu and search for it.
When Skype for Business opens, it will ask if you want to open Teams instead. This message will appear everytime you open Skype for Business so that you can either click the button to open Teams or the button to open Skype for Business.
If you have questions about using Teams, please see our Teams article here.