A very fat common utility pipe through my balcony

Hi I have purchased a flat in Pune and the flat's construction is nearing completion. A month back when I visited the site, I saw that a very fat pipe was running directly from the roof through my balcony. I checked the flats above us did not have this problem. All the other floors have their balcony to the left and only ours is to the right. First of all it looks very ugly and is an unpleasant site and second I believe it's eating into my carpet area. Now, I've raised an issue with these guys and they seem to be taking it lightly and said they'll get back to me but there has been no response for a very long time. Initially the engineering team responded saying that they cannot take my request for removing the pipe into account since " it is of Rain water pipe of Top Terrace & the attached terraces.Also it is not feasible to remove or Shift this pipe as per customer's demand.". Then I raised the issue of it literally taking space in my carpet area and the concerned person said he'll get back but no response since then. I do not know what to do and I was thinking of sending a legal notice to the builder for resolution. Please advice me. Thank you.