Avoid: Everything outside already. Don’t have, means don’t have.
Say: Sorry Sir, all our items are already on display. I’m afraid we do not have the item available if you can’t find it on the racks.

Avoid: What size you want? See here. Please don’t take out.
Say: We have all the sizes displayed on this rack. Feel free to browse around and let me know if you need any help.

Avoid: Very cheap already. Don’t believe, you go and see other shops.
Say: I’m afraid we cannot reduce the price any further.  I do believe our prices are competitive and you can count on our reliable sales support.

Avoid: Cannot try. Dirty how?
Say: I’m sorry but we do not allow customers to try these on for hygiene reasons.

Avoid: It is like this one. Other customers also use.
Say: I’m afraid that’s how it works / that’s how it’s made. If you don’t think it’s suitable, perhaps you would like to try something else.