Italian visa /regulatios

When does your PdS expire?
Janin

It expires in one week on the 26th... I received it only 2 weeks ago  ( it took 11months and 2 weeks) and that was wen they told me it's a permesso that can't be converted

I'm australian working in italy milan... I'm under contract as an english teacher at an important school teaching children.
From being extremely misinformed I have found myself in an extremely unfortunate situation, having to leave italy as my working holiday visa expires and they issued me with the wrong permesso di soggiorno.
I waited 11 months for what I was told was a permesso di lavoro.
I received my card yesterday after applying for it March 26th of last year(2017)... and with the card they told me it expires in 10days and I must leave.
Please I'm extremely desperate for information on how to go about this situation. I have a school that depend on me largely.
Can I apply for a new visa in london (if I'm an australian citizen?)
My sister lives and holds an ancestory brittish visa/passport. Could I stay with her for the process of applying a new visa?

Is it an option to apply for a new PdS based on a letter from your present employer to continue your work contract?
Or is this what the questura forbid?
Janin

Questura said it wouldnt work I tried contacting the embassy but no reply my boss has been in contact with the consulant di lavoro but they don't know what to do either .. I asked about the prefatura but they told.me don't bother? No one will really sit down and even look at the letter from my employer or my contract ... now I'm jist wanting to know the fasted way to get back or some kind or option but no one will give me a response .. they were really awful in the questura and not willing to give any options