1. Click on 3 dots on the top-right corner of chrome browser.
2. Click on Settings.
3. Click on Site Setting in the "Privacy and security" section.
4. Click on Notifications in the "Permissions" section.
5. You will see 2 different sections: "Block" & "Allow".
6. Go to the "Allow" section, find the site that pop-up comes from, 
click on the 3 dots on the right & finally disable it.