Who is Ziv?

So at the coffee shops that ask you for your name when you order so that they can call you up once it's ready, namely Aroma and Elite, I give my name as "Ziv".
I used to give out "Jess", but because there is no "J" sound in hebrew, and because the barista's don't bother putting in the apostrophe that would turn the "g" into a "j", my name shows up on the bill as: גס (gahs). Which means "rude" (masc. sing). Which is not a name I would like to appear on my receipt, especially since I go to both those coffee shops on a largely regular basis.
Also, I figure that no one under the age of 70 is named Tzvia, let alone Tzivia (my hebrew name), so I picked the modern Israeli name that most closely resembles it, in sound if not in meaning: Ziv.
This has worked rather well for me; i can confuse the crap out of the cafe workers who hear me speak to my friends and on the cellphone in english when I'm in line, and who can tell that something is not quite right with my accent, and yet I seem to have a surprisingly modern Israeli name, instead of something old-world, like Tzivia/Gitl/Bracha/Leah/Sarah/Rachel/etc... (in fact, Ziv is such a modern name in Israel for girls, that it is usually considered a boy's name, since very few girls my age are called Ziv. Usually, it's a name that will be on a five year old or younger, since it has just recently come to be more popular for girls. ). I can also maintain my anonymity and use it as my name to give out to the creepy israeli guys who seem to be everywhere, so that they won't actually call me.

However, it has recently become a problem, especially at the Elite Cafe at school. I go there so often, between nearly every class on mondays and thursdays, that the girl working at the counter recognizes me.
By name.
By my fake name, rather.
So that when I went last week with a friend from class, the girl behind the counter said "Ziv, right? You like cafe hafuch (like a cappucino, minus the sugar), extra foam, right?". And before I can smile and tell her that it's perfect, my friend said "who the hell is Ziv? (I'm Jess, and she is Reem. let me restate that very few girls in this country who are of university age are named Ziv. Also, again, it is not actually my fake name).", and then starts looking behind us.

The coffee girl is rather confused, as is Reem, as is the security guard and the coffee guy both of Aroma Cafe in the Carmel Centre, who are encouraging me to get a job there once I set up my work permit (what work permit?). Also, if I got a job at Aroma, at some point, I need to tell them that my real name isn't Ziv, otherwise the bank is never going to let me cash my paycheque. And I can't go around with a nametag that says "Jess/Ziv/זיו\גס" . And this work permit...I really need to get on that.

Oh, coffee beans...