Thanks for your guidance.
For better explanation I'm writing the whole procedure that I've come through so far.
1. I was charged for unknown landline calls during Nov to mid-Dec last year, while I was away from home. I am the tenant, and nobody else than my family resides in this property.
2. I contacted the customer service to report about the bill. The first response from the customer service was that there were definitely somebody occupying the property and making calls - the staff assured that there is no such issues like crosslines etc.
3. I checked through the security cameras and asked to my upstairs neighbours who can watch our main & garden entrances from their living spaces. Nobody broke in. (In fact it's nonsense to think of a thief makinng phone calls with my landline.) Anyway, the bill (until mid-Dec) was corrected by the staff.
4. I found that on the next bill (from mid-Dec) there were several calls made from the number displayed on my account details. This time we never left the property empty.
5. I then again contacted the customer service. Following the guidance I tried to retrieve the number of my landline, but I did not hear anything including the dial tone - which means that the landline is not even working - but I am still allocated with the landline number. The staff seemed to check who's on the line, but I don't think she figured out - this is why I'm concerned with the possibility of scam. Anyway the bill was again corrected.
6. Now I'm expecting a new bill, which again charges me for landline calls.
So, my conclusion is that the landline number on my account is actually connected to someone else's line without crosslines - that's I simply don't have an actual landline connection. So I've talked to the moderater that I'd like to have an engineer in my property to assign my landline a new number so that the one on my current account can find the right holder.
Apologies for my first post which might sound wierd.
