depending on which country you live in, you can absolutely declare before an interview that you have specified needs (i.e., not having a phone interview due to your stammer) which they should, if they're a legitimate company to work for, make adjustments for. if not, you wouldn't want to work there anyway. either way, self-declaring on an application form is also a decent way of ensuring you get an interview in the first place seeing as they'd like to fill diversity/disability quotas anyway, but that's a more cynical take!