There are two parts to this answer...
Advantage and Disadvantage Always Cancel Out
If you have Advantage on a roll, and do something that would impose Disadvantage on said roll, then the two cancel out and you roll normally. Always. Regardless of the specifics around how you gained those sources of Advantage or Disadvantage.
If circumstances cause a roll to have both advantage
and disadvantage, you are considered to have neither of
them, and you roll one d20. This is true even if multiple
circumstances impose disadvantage and only one grants
advantage or vice versa. In such a situation, you have
neither advantage nor disadvantage.
Thus, regardless of the source, if you have any source of Advantage and any source of Disadvantage on the same roll, you roll normally.
Called Shots Don't Exist in 5E
There are no rules to support them in any of the rulebooks or in Unearthed Arcana. There is no material for 5E that was released by Wizards of the Coast that includes such rules. You cannot target specific body parts in 5E's combat system. If you are playing with called shots ("I aim for the head"), then you are playing with homebrew rules. If you want to impose extra restrictions on these rules as the DM, that is your prerogative.
However, See here for an excellent explanation for why Called Shots can be a problem for use in 5E