If you don't wish to receive pop-ups you can simply follow the below steps.

If you are using Chrome on your mobile please follow the below steps:
1. Open the Chrome browser, then go to settings by clicking the menu on the top right.
2. Go to Site Settings.
3. Next Click on Notifications.
4. Here you will see a list of websites to whom you have granted permission to display notifications. 
5. Select the site you want to unsubscribe, and then click Clear and Reset. 

If you are using Opera on your phone please follow the below instructions:
1. Go to Opera > Preferences (Mac)/Settings (Windows)
2. Go to the Websites tab and scroll to the Notifications section.
3. Click on “Manage exceptions…”
4. Find the desired website → Click the “X” next to Allow to remove it from the list. (edited)

 If you are using Firefox on your mobile phone please follow the following instructions:
1. Click the menu button and choose Preferences.
2. In the Privacy & Security panel, go to the Permissions section.
3. Click the Choose button Settings button next to Notifications.
4. Select the website.
5. Click Remove Website.