Learn how to report a Snapchat user for harassing, offending, or violating the Snapchat guidelines in this article. Since there is no way to report inappropriate behavior in the mobile app, you will have to open Snapchat in your browser.
Steps

Step 1. Open the https://www.snapchat.com page in a mobile browser (for example, Chrome or Safari)
On your computer, go to https://support.snapchat.com/en-US/i-need-help and then go to step 4

Step 2. Scroll down and click Community to expand the menu

Step 3. Click Safety Center

Step 4. Click Report a Safety Concern

Step 5. Select Report a Safety Concern

Step 6. Select A Snapchat account to display a list of reasons

Step 7. Choose the appropriate reason
Further options will depend on the reason you choose. Usually, Snapchat will just tell you to block the offending account.

Step 8. Click Yes under "Still need help?" (Still need help?)
A form for entering additional information about the problem account will appear below.

Step 9. Fill out the form
Provide your name and contact information, the offending username and other required details.

Step 10. Check the box next to the I’m not a robot button

Step 11. Tap Send
Your report will be delivered to the Snapchat Security Center. If the user of this account has indeed violated the Snapchat community guidelines, the administration will take appropriate action.