讷 as nò, an exclamation meaning "Here you go"
I think the correct character might be 

吶 na4 used as an auxiliary word 语助词

We say 吶 na4 sometimes when giving someone something, so saying 吶 + the gesture of giving the thing away does translate to "here you go". The way I have heard it the most is "呐，这个给你".

However, I'd only use 吶 in informal speech with family or friends. It's quite casual and I don't think it's appropriate for professional settings, including business transactions.


  Reference Notes



In the Zdic entry of 吶, it lists 讷 as interchangeable with 吶 when pronounced ne4 which means slow of speech or to speak with a stammer (讲话迟钝或口吃). I'm guessing this might be where typo stems from. 
From the same Zdic entry mentioned above, one of the meanings of 吶 is 表示提醒注意 to get someone's attention. I think this "getting attention" + "the gesture of handing over something" combined implies the meaning of "here you go".
As an auxiliary word 語助詞, you can use 吶 in other cases without the meaning "here you go", for example "天吶" equivalent to "天啊" which is an exclamation similar to "Gee" or "Yikes" or "Oh".
吶 is commonly seen as part of the word 吶喊 which means to shout / cry out.