Могу ли я переключить свой модем на любую другую коаксиальную точку входа в доме?

It should be safe to try moving the modem to another jack.

You may have one or more splitters in your system that originate from the one line coming from the ISP. Each splitter will reduce the signal. A well designed system will try to have the same signal loss to each coax outlet. If you have many outlets there may also be an amplifier to boost the signal. The objective would be to boost the signal so that each outlet has the same signal strength as the original cable from the ISP. Longer lines will also have more signal loss.

If moving the modem doesn't work (after giving it a few minutes to be recognized) you can simply move it back to the original location.

I have my line split into two lines with one going to the cable modem and the second going to an amplifier/splitter which divides it into separate lines for the TV's (it is actually a little bit more complicated than that but that is the general layout).

As long as the drop to which you connect the modem, is itself connected to the same demarcation point or "demarc", you can connect the modem to the drop without requiring provider assistance. It seems vanishingly unlikely at best, if not theoretically impossible, for a single house to be served by multiple demarcation points, so you should be fine to connect the modem to any drop in your house.

(Source: I live in an apartment house with a single demarc, and where the coax for downstairs apartments runs through upstairs apartments such as mine. When setting up my cable modem, I found that the drop in my front room had no signal; naïvely assuming that any cable in my apartment must supply a service to my apartment, and therefore that the second cable through my front room closet must go to the unused drop in my bedroom, I disconnected the second cable at a barrel and plugged it into my modem. This got my service working just fine, but disconnected a downstairs apartment, whose occupants were most kind to me when I found myself knocking on the door to apologize for being the idiot who'd had their cable service down for the better part of a week. Were individual drops from a single demarc somehow different from the provider's perspective, connecting my modem to the downstairs neighbor's drop would not have gotten me service.)

I had to do this recently, and it is my understanding that most recently built places have a similar set-up (multiple friends have a similar setup as do family members, disclaimer: all in the US):

1. The standard in the US (recently defined standard, so may not be true of older places) is to have the input box wired into the Master Closet.
2. In there, you should have the ISP Coax and a series of other coax lines that go around your house.

My lines were labeled, but I have seen cases where they were not - in any case, buy a nice coax splitter and plug all of them in.

Alternatively you could construct a coax detector with a very low power solution at one end (audio cable, couple batteries, etc) and then in the box - the one that makes noise (with the matching receiver, either a LED, piezzo element, or whatever else) find your desired line.