Hi @ForUs88 ,
I dont have a way to change stigma that others hold - ultimately we cant change other perceptions or beliefs, but we can to things to:
A) supportively educate those willing/want to be better understanding (the "well intent")
And
B) be assertive in a professional way to services/employees that are discriminating or biased.
Its a workplace management book, but I believe some of the strategies in it can be transferred to how we talk to people in our personal lives, and especially when it comes to dealing with services - because they have a legal obligation not to discriminate. The book is called "Just Work" by Kim Scott.
This is an image from her book, which is handy as a reminder of good ways to handle (address) different types of bias/discrimination from others.

In your case, I would refer to the organisation/service's Code of Conduct and your expectation of them to meet it. Also the anti-discrimination laws if they are actually breaking those too.
I would also advise you to write down a summary of your interpretation of what they have said and the reasons they have given (especially those you feel are discriminatory biased based on stigma) and ask them (also as written confirmation) that this is a correct summary.
It gives them a change to change what they have said (which may be less discriminatory and thus a better outcome for you), or they acknowledge that is what was intent - which gives you evidence to submit then to the organisation for review/appeal/complaint if it is discriminatory.
If you'd like more info about this method and/or support in how to write something like that and finding out where to sent it to, just let me know (tag me).
This is based on not just management practice study, but also advice given to me by a Human Rights Commission Claims mediator earlier this year.