You would have had an email from PN when you joined, confirming the length of your contract. If you've renewed, the email telling you your 'product change' has been completed will have been dated the day the new contract started. Also if you still have access to your PN account in Member Centre, find your way to Account Summary under Manage Account. If there is no amount listed as Upon Cancellation after Unlimited Broadband (assuming that's what you have/had), or if there is only one months charges listed, you are out of contract.
Should you be going to an LLU or Cable provider I understand a £30 cancellation fee is payable, and any calls made during your last month with PN will of course have to be paid.
I hope that's not too confusing; I'm sure others will jump in with a better explanation, and the PN staff who contribute to this forum will have access to your account and can give information more specific to your situation.
PS: By 11/18 do you mean November 2018? If so, that's 36 months and I don't think I've ever seen an offer of a 36-month contract.
