I know you're frustrated Debbie. Did you preorder? Maybe they're having some difficulties with the company who makes the DVDs. There were some issues there with the quality of those that were sent out in February, so perhaps they're being more careful this time.
I'm a HUGE advocate for writing to customer service when you have an issue. Most places will do what they can to make you happy. I've gotten a free month of digital cable service because our cable installers messed up an appointment with me. I got a $10 gift certificate to the local grocery store because the pork tenderloin I bought was spoiled (that only cost me about $4). Free tilapia because I was bummed about no orange roughy in the store.
I am really not too "keen" on the practice of SNM having you pre-buy your DVDs. I think it would be a much better practice if they had people pre-order with a deposit the way places have you pre-order movies. You put $5 down to reserve your copy, then pay the balance when it's available. That seems a much better business practice to me.