You can chat for free with someone else as long as the other person has not blocked you. Whenever you are in a chat with someone, click on the $ to select which options and contact methods you would like to use with that other users. Some people prefer to chat only while other are fine with calls and video calls.
Remember that if you enable calls with a user and that user doesn't enable them for you, you will only be able to receive those calls but not place them. This is valid for all the different options found in the $ menu of your chats.