If you don’t feel comfortable interacting with people and don’t like fast pace, retail might not be for you. I am wondering why you took a job in a store if you don’t like working with customers. Interacting with people and moving fast is the first thing one expect in retail.

Some chains do hire people to work in the back or only do stocking shelves type of things. You could ask if they have those type of positions available. In general you might want to specify what you looking for when you are applying. When retail hires new employees, they usually expect that they’ll be flexible, unless you specified that you don’t want to work with customers.