When you subscribe, you have to buy a block of at least six concerts that come in a series. Once they've sent you your tickets, you can call in and swap out ones you don't like for something you prefer, then they send you the new tickets and you destroy the replaced ones. I've been a subscriber for about 12 years and never had any trouble doing this, but last night when they scanned our tickets they were rejected. I had to go to the box office to enquire. It turns out we had swapped out last night's tickets (avoiding MTT!) and replaced them with something else but I hadn't destroyed the old tickets. So, in fact, we did NOT have tickets to the concert last night. I was prepared to buy a pair (as we had driven an hour to get to the concert hall and were prepared for an evening of music) but the box office guy just laughed it off and gave us a free pair, which was very nice of him. With the pandemic situation, the concerts are only about two-thirds full, so there were plenty of seats and, as I say, we're long-time subscribers, but he didn't have to do that.