OneStopPlus.com False advertising and coupon code not honored Internet

OneStopPlus failed to honor their own 20% "Off your entire order" coupon they emailed me. I was placing a good size (over $50 order) and my coupon code wouldn't take so I called them up and asked them why. The (rather rude) lady on the phone stated the coupon was only good for orders over $75. I told her NO WHERE on the coupon does it say this and it should be clearly marked! She treated me as if I was stupid and had me read off the entire coupon over the phone. After she realized it indeed DIDN'T mention that anywhere on the coupon she told me to click on the tiny "OFFICIAL RULES" PDF manual linked at the bottom. Who in there right mind expects someone to read through a lengthy official rules manual to confirm that the coupon is even able to be used? This is a clear and blatant case of FALSE ADVERTISING / BAIT AND SWITCH tactics they seem to be well known for. I've sent a complaint into them but I do not have much hope that they will actually do anything about it. I have a hard enough time finding clothing my size and I do not need to be treated like i'm stupid on top of it. All I ask is that they be clear and honest with their coupons.