It's showing that your phone is currently set up to work with a text phone device for the deaf.
A phone atop of seven small dots means that it is set to work with TTY. TTY, also known as Text Telephone Device or Telecommunication Device for the Deaf (TDD), is a special device required at both ends of the conversation that enables people who are deaf, hard of hearing, or speech-impaired to use the telephone to communicate. TTY works by allowing people to type messages back and forth to one another instead of talking and listening.