Text notifications from 32665 is not a scam. If you've set up Instagram texts, you can use 32665 (FBOOK) to get notifications without using mobile data. Keep in mind that standard messaging rates apply. You may need to use a different code from 32655 (FBOOK), depending on your country and carrier.
If you want to stop receiving notifications from 32665, you can send "STOP" in a SMS text message to 32665.
A 32665 Instagram Text Notification
Text: X is your Facebook password reset code. Reply "stop", or go to https://fb.me/XXX to turn off SMS messages for your Facebook account on this mobile number.
Although texts from 32665 are not scams, scammers can spoofed the telephone number. This means they can send phishing texts from other telephone numbers and make it appear as if it was sent from 32665. Therefore, it is recommended not to click the link in random texts that appear to be from 32665, just use the code if you have initiated the request. And, never send the code or give it to anyone.