I'm not sure if this is a resent thread but I had the same problem with my DS.
As he can't hear when there is any background noise shopping was a pain.
I could not talk to him or find out what was wrong.
After we got a few signs under our belt I hoped it would be better but no the issue.
We tried most things until I was told to give him a job.
"Mummy is shopping why do I have to be here!!!"
So before leaving we would write a list of jobs for him to do while I am shopping. Find out the price of ... What is next to ... on the shelf. How many toilet rolls are in a packet
We made it a game for him and I made the questions around my list so I didn't have to go out of my way and make the trip longer. I had to make a fair few questions for the checkout or it would all melt down again.
This has saved my sanity as I home school and don't get days off or respite care. It is also a game I can use to teach him. Reading, writing, math. He love the calculator now and I never go over budget!!