A: I already gave you her phone number.

B: But it's the wrong number.

A: Ok, then I will ask her and tell you a correct number.

Q) Is this correct? The wrong number, a correct number ? (I want to know the correct use of an article)
It is a quirk that we often say "the wrong number" when it's one of millions of wrong numbers.

Definitely and logically, "the correct number" but somewhat illogically, it's also "the wrong number."

No it should be the other way round.

Because you can have as many wrong numbers as you want but the correct number is just one.

In much the same way, we say tell a lie and tell the truth. Because there is one truth.

 BarbaraPA's reply was promoted to an answer.