There is aknown issue on the Members Centre Dashboard regarding the contract dates etc. shown there. It is due to be fixed at the next "update" of the page so I have been told by Plusnet.
As for your own contract end date, with luck a Plusnet staffer will see your post here and be able to advise you. Otherwise have alook in the member centre> manage account>account summary. The latest contract you entered into should be there with its start date.