Is it on a piece of paper?

Read the rules of the building and your tenancy rules...
They force you to buy a similar looking tag.
Welcome to Switzerland!

By the way, it will cost easily 60chf, so I suggest you buy one online in a chinese website (with similar design) and import it....

It might be your caretaker / Hausmeister / Concierge that is cleaning your box.

Many Swiss believe paper name plates look cheap. Do the other boxes have nicely engraved metal plates? Maybe you need to get some exactly the same as theirs? The rule might be in your rental contract or house rules.

Your Landlord will order them for you, cost CHF 50 to 70, but you can take them with you when you leave, for the next post box. I have three sets, all different sizes and styles!

Mine cost 26chf (including the clip to hold it in place) which was cheaper than I was expecting.

Fortunately our landlord didn't mind having paper stuck to the box for two weeks until we had the proper one made.

Just find a shoe mender / key cutting shop and they will make the plate for you.

Put another piece of paper next to the name label with:

Mailbox Rules
1. do not remove paper labels from mailboxes

Whoever it is will not be able to disobey a rule and your name label will be safe...

(might only work if you translate it into Swiss German or French or whatever the local language is)

Also get a proper mailbox name plate made... they can do it while you wait (or maybe in a few hours if they are busy)

Also, once you have the proper name plate keep putting a paper one on every day anyway

Welcome to Switzerland.

Learn quickly that you need to put your foot down and not tolerate any shit from these people.

Normally, the landlord and/or agency will arrange these name plates for you and send you a bill. Around 60chf as mentioned, unless you have some awfully long name.

Speak to landlord and/or agency and explain, that you need to arrange name plaque, do/can they assist, explain the need for your to have some and ID on the box so you can receive post and and in mean time leave a note stating something along the lines of:

"Dear kind neighbours, I have recently moved into the area and waiting for my name plaques.
As I need to receive my important post in the meantime, I NEED to have my name on the post box in some format. I am unsure how or why this could possibly both you.
Please leave the name tag there until I receive the appropriate plaque.
If I find out who has been removing the name and causing me unnecessary stress and non receipt of important post then I will crush your testicles in a vice and stamp on your head. If you are a woman and doing this, then do you know how deep lake zurich is?"

It's worth mentioning at this point that the cantonal law (at least valid in VAUD) that the renter has the choice of manufacturer to make that plate name.
I was charged 60chf to "comply" and I did not know that law at that time.
But you are free to buy your own plate on any place, I guess it will be much cheaper.
After all it's about 2 tags names (1 for mailbox, 1 for door) and it's cheap.
Only issue is to have to comply to their style... but its standard forms!! just take a picture of the other neighboors plates

Piece of paper is not a problem in my apartment bcoz so many ppl use it only. My husband has been here from december, before it didnt happen. All this is happening from past 2 weeks.Anyways thankyou for the advice

I enquired with few local neighbours in my apartment. But they told no caretaker removes it. Its nothing like that in contract also.Other letter boxes look more rubbish.

Someone hates you.
It is NOT NORMAL for anyone to take off name tags , paper or otherwise.

Call the police or inform the hauswart.
Or owner.

I made a note in german. But it was torn off into bits

We never talked with anyone except hallo n tchuss. I told the owner but its no use.

Call the police, ask them to come around, lights flashing....to let all neighbours see it.
Better still, ask them kindly to pen a letter to all the neighbours...

This is called shock therapy.

someone did the same to my post box in zurich when i had a " no junk mail" sign so i laminated the sign, and taped it to the box - someone kept taking it off so i glued the edges down - its been there for 2 years since.

what happens if you use selotape to stick the name down?

Rub dog faeces around your name...

Videotape the culprit and kick his/her butt:

I was going to suggest something like this actually. Good idea. Perhaps coat it in anthrax too so anyone who does try remove is screwed!

But in all seriousness, if possible, as much as it will be a long boring day potentially, sit and watch from a hidden view point, and when you see who it is confront them. If the person is Swiss they will shrink so quickly they will possibly soil their pants on the spot.

They will then complain about you, say you are rude and that you do not follow the rules.

But seriously, do not fret. In time, you will begin to take comfort in these small issues that cause them so much bother and smile at the fact that people do have lives as mundane as this and thank the lord its not you. (if your religious that is)

If the letter you are expecting is so important why not write your name with a permanent marker?

I use selotape only then also its being torn.

Has there being a death there recently?
A poltergeist? One who does not want you to live in her house?