All interactions coming from any channel are stored in the Customer Journey, which can be accessed from the Contacts Manager or from the Channel Interactions List (open the interaction and shift right to the last tab Journey of the Info area).
Any time the Agent manages an interaction, the history of all the interactions of that specific customer can be shown in a timeline.
Each interaction type shows up a different colored icon according to the Channel used and can be opened clicking on
(available only for those Agents with proper permission on the specific item) or inspected clicking on Show Details:
Here you can see information like: Created/Closed At, Subject and Disposition (if there are, all levels of them).
You can select the interactions by channel and by date/period using the filters on top of the list.