Can Jewish people use telephone on Saturdays?
Firstly, in this question there is a misunderstanding of the
'day' of the Jewish Sabbath.
Saturday is commonly believed among non-Jews to be the Sabbath.
This is incorrect. The Jewish days begin at sundown. The Jewish
Sabbath begins at the start of the seventh day of the week.
Therefore, the Jewish Sabbath begins Friday at sundown and
continues until one hour after sundown on Saturday.
If one lives in a city where the sun sets at 3 p.m. on Friday,
then the Sabbath begins at 3 p.m. on Friday and continues until 4
p.m. Saturday. If the sun sets at noon on Friday...; etc.
Now, to answer the question. Jewish people cannot use a phone
(to receive a call or to make a call) on the Sabbath. Once the
Sabbath has passed, yes, a Jew can use the phone.