I am sorry you are going through that. for me there was no stress over when people called my alters the body name. you see my system was one where the abusers constantly told me to ....do not tell, this is a secret game, do not tell anyone. as a result of this abusers code if I did tell anyone I knew worse things would happen, (I would go more into detail but dont want to trigger anyone)

my point is all my alters answered to the body name too. this ensured that no one would know that they existed, which meant no one would know that the abuse was happening.

I have been this way since before I was 5 yrs old on up until all my alters integrated. so for me that meant being called by the body name was my normal, it actually felt very weird to me only after I grew up and got diagnosed with DID. after diagnosis sometimes I would become aware during a conversation with someone calling me my alters name. not weird major problem just a quick realization wow did they just call me rainy, hmm ok that was weird but its happened before more on and answer them.

also most of my alters names were names that others have given me through out my childhood.. example sunny actually got her name from a favorite uncle who said he loved my smile one day at the beach.

my point again is whether I was called the body name or the alters name it was pretty normal for me since before I was 5.

that said I do know some who after diagnosis prefer to be called their own individual names. one of my friends they "field" questions by having blanket statements ready...

using your example of birthday instead of just saying July my friend says...

well I actually have 2 birthdays, the one I was born with is this day and the day I have chosen to celebrate is in July. I think July is such a nicer month than this dont you?

this turns the conversation away from embarrassing and conflicting questions to a topic that is nice and calm for all.

suggestion maybe since you seem in your posts to have co consciousness of the others maybe you can all come up with blanket statements that will make the situations less upsetting like my friend has done with her system having more than one birthday.