a was left out. You always put an a before a name.
Not in this case. The subject is "Yo" me llamo Antonela. = literally "I call myself Antonela" but translated like: "My name is Antonela."
Sr a
The subject pronoun that has been left out of this conversation is "Yo" (I). In Spanish, it is common to omit the subject pronoun when it is clear from the verb conjugation or the context who is performing the action. In this case, "Me llamo Antonela" translates to "My name is Antonela," so the subject pronoun "Yo" (I) is understood but not explicitly stated.