So you dont have a typical phone line to your apartment?
Does it go through some sort of PABX? So you cannot choose your own pots landline provider?

Try picking up the phone and dial 1956 and tell me what happens - if its a standard landline running on the neax at the telecom exchange, then it should read out your telephone number. You should then just be able to get broadband on this line from a provider that doent require you to have pots or tolls with them.