I've come across this before with other companies.
In fact I was calling one particular company who wanted to speak to my FIL as the account was actually in his name. (Don't worry, this was all above board!) They wanted to confirm with him that I could act on the account so I just put Mr P on the phone instead and all he had to say was "yes, 2sp can act on the account". They didn't even ask him any security questions!
They shouldn't assume that someone sounds like their gender are "supposed" to.