Half simple character lets you make calls (3,4)
I believe the answer is:
sim card
'you make calls' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.
'half simple character' is the wordplay.
'half' means to take half the letters.
'character' becomes 'card' (both can mean a humorous person).
'simple' cut in half is 'sim'.
'sim'+'card'='SIM CARD'
'lets' is the link.
Can you help me to learn more?
(Another definition for sim card that I've seen is " Storage device".)