One time I sent dh to get me flat rate envelopes and the ones he brought home were not flat rate. I didn't even notice (or think they made them in a non-flat rate variety) so when I went to send something, they charged a bunch more shipping. DH didn't know so he paid it but boy was I ticked. They said it wasn't a flat rate envelope but THEY are the ones that gave them to dh or told him where to find them. I just wonder if he said he needed a flat rate envelope and they pointed to them and there were some non-flat rate mixed in for some reason. So now I always check.