The attached number is a 24/7 support service run by the Ministry of Health, that connects people with trained counsellors.
The message appears to be rolling out to users all across New Zealand, but some have not seen it yet.
Social media platforms including Facebook, Instagram, Youtube and Twitter have been heavily criticised for their slow response in regards to the livestream video of Friday's attack.
The video was continually shared on the social media platforms before they were able to shut it down.
Facebook said in statement that the shooter's livestream was viewed fewer than 200 times and was not reported until 12 minutes after the 17-minute broadcast ended. The company says the video was viewed about 4000 times in total before being removed.
The company also said that their artificial intelligence was part of the problem.
"While [AI's] effectiveness continues to improve, it is never going to be perfect," Facebook said in a statement on Thursday night.
"People will continue to be part of the equation, whether it's the people on our team who review content, or people who use our services and report content to us."