People at volunteering making me feel bad

There’s a guy who volunteers at the charity shop who keeps only talking about using the till to me. The manager told him to stop a few weeks ago (after what he had said to me made me have a mental breakdown) but he still does it. Literally as soon as I walk in the shop, every week, he starts asking if I have used the till since last week and making me feel pressured. Today I stood up for myself and told him to stop. He kept apologising and saying sorry for upsetting you (he says this every week but then carries on talking about the till to me) but really? How many times does he have to be told?
I am very mentally unstable so working on the till is not my priority. I only volunteer to get me out of the house and to do something ‘positive’!

Then, a lady there who I thought was my “friend”… well I have only known her for 2 months but her birthday is coming up so I gave her a card. Today she was complaining that I didn’t put any money in the card like someone else did!

I am so annoyed. This charity shop is for a mental health charity but some of the ‘staff’ there make me feel so s***.
I am really considering finding a different place to volunteer.