In Brazil, there are regional variations and word/phrasing variations as well.

Formally:

• "Você ligou para o número errado" (you called the wrong number)
• "Você discou o número errado" (you dialed for the wrong number )
• "Você está ligando para o número errado" (we call it the "gerúndio", something like "-ing", as in "You're calling the wrong number")

Informally/casually:

• "Discou errado, irmão" / "Discou errado, mano" / "Discou errado, cara" / "Discou errado, mermão" ("dialed wrongly, bro", with "bro" variations across Sao Paulo and Rio de Janeiro (the latter being the latter variation))
• "Tu ligasse errado, visse" (some Brazilian northeast states, something like "Thou calledsth wrongly, see?")
• "Né aqui não, moço" (Minas Gerais, something like "It's not here, boy")

There are lots of other variations and I'm not really aware of all of them.

Also, the way I answer depends a lot on multiple factors such as: my emotional state (wrath? Sad? Okay? Excitedly happy (rarely)?), my current pace (rushing? Chilling?), among others. Generally, "Não é aqui não" (the Minas Gerais variation without the ending "moço" and a fully spelled "Não é" instead of "Né", because I'm originally from interior of São Paulo state but highly culturally influenced by a part of the family from Minas Gerais).