Wanted to update current subscription, instead it created new "parallel" subscription.

I just got the MacHeist bundle that included Parallels Access (1 year subscription). I figured that I could simply add the year to my current subscription. After some rather involved searching and following links, I found where I could enter the subscription code. However, it seems to have created a new 1-year subscription rather than added the year to my current subscription. I don't need two subscriptions, particularly when their subscription periods overlap. How do I merge the two subscriptions, i.e., add that extra year to my current subscription?

Thanks!