I can't talk to you now. I'll talk to you later when _____more time

I can't talk to you now. I'll talk to you later when _____more time

Explanation

"I can't talk to you now. I'll talk to you later when I'll have more time."

This is because it is future tense,

The use of "I'll have" conveys that you will have more time later, allowing for a conversation.