Either one is ok. We know exactly when the person called the wrong number - it was when you heard the phone ring, right before you picked up. The present perfect tense ("you've called") is fine because you know this action was in the recent past, and the present perfect is commonly used for recent past actions. The simple past tense ("you called") is also fine because again, we know this action happened in the past (the recent past, but still the past). There is only one past event here, so you don't have to worry about using different tenses to make the order of past events clear, which is often a reason to use different tenses. For instance: "You called me yesterday, at which time I told you this was the wrong number, but you've called me ten more times since then!" - in this case, the present perfect indicates an ongoing action that might still be happening now.
EDIT: I will also say that I agree with David Siegel that "Sorry, wrong number" is a more common response when someone calls you accidentally.
EDIT 2: Mazura also has a good point - you are probably more likely to apologize if you are the one who has dialed incorrectly.
From Google, you already know which one is more common. Perhaps, you want to ask why people might prefer the present perfect as opposed to simple past tense. – urnonav – 2019-04-26T17:54:41.750
Personally, I'm quite shocked by the fact that the sentence implies that there is a single wrong number that everybody calls. I say "a wrong number", whether I prefix that with "you called" or "you've called" or "you have" or "you've got"... and incredibly enough, Google tells me there is only a single match on all the Internet for "I think you've called a wrong number". However, when you remove the "I think" (you can be polite and say I believe, you must...) you get many more. – Law29 – 2019-04-26T22:28:40.673
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@Law29, in other contexts, e.g., the phrase "you've picked up the wrong briefcase" using "a" in place of "the" would definitely sound wrong. Your version seems more logical, granted, but it isn't idiomatic. One possible explanation. Another one. Oh, and several answers here.
– Harry Johnston – 2019-04-26T22:40:34.090You forgot the even more popular third option, "You have the wrong number." – John Wu – 2019-04-27T02:33:50.487
True story. "I'm sorry, you've got the wrong number" - "Then why did you answer it?" – Dawood ibn Kareem – 2019-04-27T03:25:51.563
@Law29 "A number that you called is wrong" and "The number that you called is wrong" have different meanings. In the OP's sentence the caller only called one wrong number (and the speaker knows exactly what it is, namely the number of their phone.) There is nothing wrong with using the definite article "the" to refer to a single well-defined entity. – alephzero – 2019-04-27T10:33:33.103