Mattress Firm review: accurate size of king mattress

Purchased a beautyrest pillow top mattress (standard king size 76x80) - known and listed on website. Received mattress it is 74x77 inches. Called got a lady Crystal who was useless, said she emailed her manager Sean, I call speak to Sean he acts clueless. Thank god for Roy who atleast understood. They say a mattress can be 2 inches smaller each way, I never heard of this and advised it should be stated in a disclaimer if this is so, website says 76x80. Roy was able to speak to his district mgr, they sent me another mattress, it is no better. I decided to measure the frame it is 77 inches long..how can you sell a King bed for 3 inches smaller and not advise your client. I am seeking to return with no charges to me as I feel I was falsely sold a king bed. you are charging me the price and not supplying the product. Got another idiot that told me it can be 5 inches smaller I told him call his district mgr he may disagree with him. Whatever, lets see if Roy can get me refunded with no fees. I will not use Mattress firm in the future.