I've done dozens of these, it's the easiest money I've made doing shops. It only takes 10 minutes tops to do. If I were you I would get as many of these shops that you can get your hands on. You don't need a letter, just stop at the service desk and sign in.
I'm curious, can you say what company it is? If it's a different company I want to see if I can get some shops from them.
Thanks
It's not easy to see. Look around the cube and you'll see a hinge on one corner. Open the door on the opposite side and you're in. BE VERY CAREFUL OPENING IT !!! When I opened it at one store about 100 card fell off and I had to sort through them and put them back.
I've done dozens of these shops, I've never been given a Walmart badge. OOPS!
Generally WM only gives you a vendor tag if you will need to go into the back room. Your badge issued by the MSC is sufficient for the restock work so long as you sign in.