This is WHY stores have signs up on display. So you know the rules BEFORE you buys things.
Your just not that special to think these rules do not apply to you. You say your embarrassed to explain your disease (of which I've never heard of, maybe you actually mean you have "motor neurone disease" ?? to one shop assistant who is there to help you and I am sure would have been discreet. Yet you have no problem plastering it over the internet for every person to see.

Store credit for you buddy.

i visited your westfield Kotara store to look at purchasing some dress pants, i am unable to try on in store as i have a motarnurone disease which room in change area is too small and unable to try on successfully and dont like discussing my embarrassing medical issues with any one including shop assistants , i told assistant i will try on when home as that is more suitable, for reasons given to you earlier, the pants did not fit and do not do the job i was searching for, i returned items still with tags , un worn perfect condition and with receipt, to be told NO REFUND and i had only 2 options and pointed to your sign, it says no refund for change of mind is that correct,!!! these were brought back because they did not fit and do the job required of them due to the cut of the pants as described to the assistant also,there were no other items that would fix the fitting issue, he repeated 2 choices only, i told him to put them back in the bag with the receipt,i took a photo of your sign and taking it up with consumer affairs.i believe my request was fair and understanding , i am not a rich person to have money tied up in that store especially when nothing was there that would do what i needed, regards Mark my number is 0401 233 512