No there is NOT a voltage adjustment for black level in digital video displays. If you think that is true, you are not understanding some of the fundamentals of calibration. In the old days of analog video with CRTs, there was a voltage level that controlled how black the display was (among other things) but you typically would adjust that by eye (looking at a PLUGE pattern on the display), not by setting it to some specific voltage.
In a digital video display (you did not even include enough of the model number for any of us to determine whether you are talking about a plasma TV or LCD TV, but both work more or less the same way), you display a PLUGE pattern and adjust the Brightness control to get the black level set correctly. No video displays made today have "perfect" black when displaying black video information. A couple of plasma displays (Gen 2 Pioneer Kuros from several years ago and a few new Panasonic plasma models) come very close to having very very very black blacks, but other plasmas and all LCD displays have a black level that isn't perfectly black. There is nothing you can do about it other than purchase a better TV that offers blacker blacks.
A PLUGE pattern usually contains "below black" plus black plus a third level that is a little above black. You adjust the Brightness control to get the black part of the PLUGE pattern to match the "below black" part of the PLUGE pattern so everything at or below black is as dark as the display can make it.
White level is set by the Contrast control. Once again, in digital video displays, there is no "voltage" you set for white level. You set Contrast to achieve a 100% white level of around 35 fL in a dark room. If you have no meter to perform this measurement, you are just guessing. Using a test pattern with digital values of 200-245 will show you whether the TV clips or not... some digital displays do, some do not, actually, these days, many digital displays do not clip white levels. But whether or not the display clips white levels doesn't necessarily have a lot to do with whether you have 35 fL or a headache-inducing 70 fL (when viewed in a dark room). All you can tell is what setting range you can use before clipping begins. If you look at the Contrast control and it has a range of 0-100 and you always see levels 200-254 no matter what Contrast setting you use, that TV just does not ever clip. But you still no nothing about how bright the TV is if you don't have a meter. Your only "tell tale" about whether Contrast is set too high is eyestrain. If you watch a movie for 2 hours and you detect a feeling of eyestrain, chances are the Contrast control is set too high. If you can watch a whole movie in a dark room without feeling like you have eyestrain, your Contrast control is set either correctly or too dark. The only way to know if it is set too dark is to raise the Contrast control and watch another 2 hour movie and see if you got the feeling of eyestrain... if you did, Contrast is now too high and it should be lowered. Learning the best Contrast setting without a meter can take some time... probably weeks of trying different settings and viewing content for 2-hour stretches to see whether you are comfortable or not.
It really sounds like you need to learn a lot more about calibration before you go looking for adjustments or settings that aren't right in front of you in the User Menu.