It's the colloquial answer to the question “Will you call me?”. Você irá me ligar? (formal) Me liga depois? (colloquial) The answer to this question is “Yes, I will”. Sim, irei! (formal) Ligo, sim! (colloquial) People often use those couple of sentences (question-answer) when they don't have time to talk everything they want at that moment. So when they are saying good bye to the other, if they want to continue the conversation or they have more subjects to talk about, one of them could ask the other to call him/her later. That's the common situation to use those sentences.

O verbo ligar pode ter três significados: Ligar = chamar ao telefone Ligar = dar ou não dar imprtância (a alguem ou alguma coisa) Ligar = juntar

It depends on the context. Besides these meanings above (to call), the verb "ligar" also means to care about something/someone, as goes: — Will you call me? (Você vai me ligar?) — Yes, I sure will. (Ligo sim!) — You don't care about what I tell you... (Você não liga para o que eu te digo...) — Yes, I sure do! (Ligo sim!) *This last meaning sounds a bit colloquial to me. Hope it helps.

It depends on the context. Besides these meanings above (to call), the verb "ligar" also means to care about something/someone, as goes: — Will you call me? (Você vai me ligar?) — Yes, I sure will. (Ligo sim!) — You don't care about what I tell you... (Você não liga para o que eu te digo...) — Yes, I sure do! (Ligo sim!) *This last meaning sounds a bit colloquial to me. Hope it helps.

When you say "ligo sim", it means that you are confirming a request of someone else, like ? . Will you call me for sure ? . Yes, I will ( ligo sim )