Other accounts linked with the same phone number will not be able to edit the notification settings.Each account that has your phone number associated with it will still receive SMS text messages for password reset requests or security features like login verification.It’s important to note that only the account most recently linked to this phone number can perform SMS commands and receive SMS notifications for account activity like Direct Messages, new followers, Retweets, etc.
If you received a message that the number you are trying to attach to your account is already associated with another Twitter account, it’s possible that your phone number previously belonged to someone else. This only means that outdated information still exists in the system.
It has grown beyond alphanumeric text to include multimedia messages (known as MMS) containing digital images, videos, and sound content, as well as ideograms known as emoji (happy faces ,sad faces ,and other icons).
As of 2017, text messages are used by youth and adults for personal, family and social purposes and in business.
Read more about adding your phone number to multiple accounts here.
An accurate and up-to-date phone number and/or email address is an important step you can take to ensure you never lose access to your account.