Blizzard’s responses aren’t automated.
That is in their policy, they can’t subsitute quest rewards. You’ll have to be more careful next time. It would be much easier to just swap ther reward for you, but they simply can’t because of policy.
Customer service =/= complying with all of the customer’s demans.
As a side-note, I would not recommend opening 18 tickets for the same issue. You didn’t make the distinction of whether or not those 18 ticketes were about this same “quest reward” issue, but I am hoping they were mostly seperate issues.