wake-up call
US /ˈweɪk.ʌp ˌkɑːl/
UK /ˈweɪk.ʌp ˌkɑːl/

1.
a phone call made to wake someone up at a specific time, typically in a hotel
:
•
I requested a wake-up call for 6 AM.
•
Did you get your wake-up call this morning?
2.
an event or situation that causes people to realize that they need to change their behavior or attitude
:
•
The recent economic crisis was a real wake-up call for many businesses.
•
His doctor's warning about his health was a much-needed wake-up call.