Today I am learning words connected with shopping. Could you check this for mistakes, please? Thanks

1. Could I try this dress on?
2. You should try this dress on to know if it fits you.
3. Just try these shoes on for size! We will decide later about their price.
4. Don't try it on! I hate lies. ??? Can't see how the second sentence relates to the first. Are you sure you mean lies?
5. If you would like to try this item on, you should turn right and there you will find several changing rooms.
6. Jane likes going shopping because her father pays for all her purchases.
7. Would you like to pay with cash or credit card?
8. Sometimes people who order something online spend less money than those who go shopping in malls.
9. My mom doesn`t like completing an online order form by herself. Usually she asks me for help.
10. I would like to return an item because it is too small for me.
11. Can I get a refund?
12. Here you are. Please get a receipt. I understand from this that money is being given to someone so that they can pay for something and that the person giving the money wants a receipt. If this is what you mean, then these sentences are correct.
13. I am sorry I have noticed the rejects (waste) on this skirt. I am sorry but there is something(/are several things) wrong with this skirt.
Last one, I did not understand the meaning “give a customer store credit”

If you give the customer store credit it means that they do not pay straight away but can pay later (often in installments).  Generally a customer opens an account with a store and receives a card which they use to pay for things in that particular store.  They then receive monthly statements and pay off the debt over time.