When a shop gains rank, you can gain levels on the options. One helps you be able to sell to customers better with a set of commands that as far as I can tell, are no where in the game. Then again, I'm stupid, and just haven't found how to bring up those commands?
There are two different things you can gain.
When you gain a badge (sales for example) you will gain a new sales specific skill. This will be available anytime you click on the sales option on a customer.
They are basic sell, offer at cheap, hard sell, and then dazzle.
The other way to gain skills is through the rank/reward points.
The first two skills do not show up under the sales tab, they show up under "assess" when you click on a customer. The later skills under "manipulate"
They should all be there as soon as the sim finishes their convoluted and torturous path to get into the shop, and either starts looking confused or moves to browse.
Are you missing all the sales options?