This surname has over 200 listings in the online phone book for Lithuania. It is virtually impossible to determine what town a family was from by its surname only. You will have to find records (naturalization, death, birth, marriage, ship manifests, etc.) with that information on it. The name alone will not be enough.
The surname is pronounced in Lithuanian vih-SOTS-kihs or vih-SOTS-kahs (the latter is the more common spelling).
The endings to surnames change for women depending on whether they are married or not. For married women the husband's surname ending changes to "-iene" so the wife of Mr. Visockis/Visockas would be Mrs. Visockiene. For unmarried women, her name ending changes depending on how her father's surname ends. If it ends in "-is" then her name ends in "-yte"; if it ends in "-as", then her surname ends in "-aite." So the unmarried daughter of Mr. Visockis would be Miss Visockyte; of Mr. Visockas, Miss Visockaite.