Ordering additional devices

WHY does this company make ordering additional items so difficult ? I attempted to order during the Memorial Day sale for 30% off additional devices, and it keeps making me check out with only 10%. I take additional time to call in, and then they tell me that things are out of stock so they will cover a month of monitoring only to find that I have to CALL AGAIN to get it. This has been a historical issue when ordering with advertised sale prices/discounts. Does anyone know why they make it difficult to order additional devices ? Anyone else have this issue ? Even trying different browsers does not resolve the issue. Then when you take the time to call in, they can't help and all the do is confuse you. They must not want to keep long term customers.