Not holding stock for subscription

Have a box at my local CNA that they place each installment of a bi-weekly book series. Today when I went to check my box I found that they had not bothered to put the last two issues in my box. Their excuse was that the person who usually does it was away. The books are now sold out and I cannot get the ones I missed. I have bought 21 books in the series so far from that branch and am very angry that nobody bothered to do their job and keep aside the stock that was promised to their regular customers