I'm only been waiting for two months now, but I can definitely appreciate the tension involved. Sadly, I don't think that calling will help at all, since it hasn't been 6 months yet, so as far as the IND is concerned there's nothing to complain about. What I would do though is start filing a request to get your passports back. You can ask them for this, and they'll just note the info they need (or maybe make their own copies). I think that you'll have more success accelerating your application by asking them for the passports, which would draw attention to your dossier, rather than asking for the citizenship to be completed. Think of it this way: bureacrats don't like their power questioned and they get fussy when they think it's being done. Asking them for your passports is, in their mind, a legitimate request that doesn't undermine their authority. Asking them to do their job faster, however, does. Do you see what I mean? It might be more strategic to ask for something do-able that might have the same effect.
I sent in certified copies of my passport, so, alas, I don't have that option. Good luck!