sounds confusing, alright.
I've used these plans before and run out of time before the enddate and wanted to renew.
I cancelled, waited awhile and then returned to site to see that the plan had been cancelled...ie: given their site time to refresh. Then, I started a new plan with no trouble.
Hopefully they haven't changed the possibility to do this but in any case, what have you got to lose? Cancel the plan and then start a new one.