。
Why didn't you call before you came?
Literal
Come before [at-に] why telephone [object-を] put-give-me-not-[sentence-ending-の].
The sentence-final の (here with rising intonation for a question) is a casual conversational question ending — softer and warmer than か. ~てくれる is the 'do for me / give me [the action]' auxiliary; negated ~てくれなかった = 'didn't do [it] for me.' A gentle reproach.