Billed for 6 months of water bills at once

I am currently renting and have just had an email sent to me from my landlord with an invoice of 6 months of water bills ($300+) with one week to pay it.

We were never sent monthly water bills by our landlord which was the case at my previous flat so I did expect a chunk of it to come at once but I also expected some warning and not one week notice to pay.

Will we be held accountable to pay for this or is there a valid argument that he did not warn us or discuss anything to do with our water bill and so we can get out of paying it or at least get more time to pay it.