If you open the most recent alert that has been sent to you and scroll down, you will see a "cancel alerts" button. If you click on that button, you'll be taken to the "alerts" section of your account where you can cancel your alerts.
Alternatively, you can log into your account directly and cancel your alerts. Please click on the drop down under the profile icon and go to "alerts". You will be able to remove any alerts that you've set up there.