@Vibha11
I have never come across any complaints department or procedures at Airbnb. You would think that such a thing does exist but they make it very hard to find! Perhaps some other hosts know how to reach a complaints department...
Alternatively, there are often external agencies/ombudsmen that you can lodge your complaint about Airbnb with, but that will depend on your location.
However, you have not said what your objective is here. Do you just want to complain about how the situation was handled? It does sound like a nightmare, but Airbnb customer support is very hit and miss, so the poor level of service you received is not uncommon. Of course that doesn't make it okay.
Or, are you hoping for some sort of compensation? I really doubt you would get that as it sounds like you managed to find the Airbnb and complete your stay (not sure if you were able to sort out the additional fees for extra guests, if there were any, with the host). I am pretty sure Airbnb doesn't offer any compensation for poor customer service. If they did, they would probably be bankrupt. It happens so often.