Where do I find Call?

Open the menu (☰) from anywhere, including the character-selection screen before you've started. Call has its own row in the main list directly under About Me, labelled Call with a "(voice only)" tag, and it also appears as a tile in the Talk section of the activities menu. Tap it to open; tap the ✕ (or pick anything else from the menu) to leave, and you'll return exactly where you were.