Hello @Vladek 

Did you order DSL?

Can you place a picture of the cable here so we can have a look?

Hello,

I didn't do anything so far, but it's clear to me that when package from T-Mobile will arrive it would be impossible to make connection because there is no socket

@Vladek 

Not sure if this is the right cable, are there wires in it?

But yeah I think it's better that T-Mobile send a technician.

Yes there are some wires inside. Guy that did renovation of the house said that this is the internet/TV cable

It looks like a coax cable to me… Maybe the previous owner had internet / TV via coax cable? 

No idea ...I know for sure that previous owner was a big mess)))

WhenI'm back home I can take closer look and to make more photos ...if it helps to find out what that thing is