Please see the below answers for proper translations - for a guide on how to find words easier and my translation, continue reading :)

Okay, the golden rule of learning Dovahzul - the translator does not exist! As useful as it is, it's buried with non-canon and errors. Instead, you should use the Search tool or the Dictionary

Using the search tool, click on Dragon Word and select English definition, then type name into the box, keep all words as it is, click canon and select Non-Canon.

After that somewhat exhaustive exercise, you should see one response:

My translation of "That's not my name" would rely on the fact that "Zu'u kallum" means "I am callum", so it'd be Daar ni zu'u, literally translating to that not I. It should be important to note that I've not mastered Dovazhul, so don't take that translation as the gospel truth.

Not all verbs can be their noun counterpart, and not all nouns can be their verb counterpart. See Honaat and Honit.

@Callum

Wouldn't Tol ni zey be better because it translates to That(s) not me?

Also, Tol ni dii faan would be another good translation, translating to That(s) not my name.

One more note, Tol is That, and Daar is This.

Edit: I have been informed that Daar can be this OR that and that Tol is used as a conjunction.

Adding to that, (as a general rule) any verb can become the corresponding noun and vice versa. In this case, you might get away with "dii faan los..." for "my name is...". It's not agreed upon if this is good Dovahzul, but at least this translation is unambiguous.