swift vector
from what's above i got the sense that you are using a helpline in a country that itsn't the most accepting so you are looking for advice of getting the pther person to use your prefered name. if this is the case, i'm unsure how helpful this is but maybe just starting the call with "my name is [insert name]"
please tell me if i got something wrong from above
in terms of excuses, you could say that your voice was strained or that you hurt it somehow. i'm not sure how much that appys to a voice being higher pitched but it isn't uncommon for people to temporarily hurt thier voice. anther option is to fake recovering from losing your voice, which would let you whisper and would probably sound less feminine because (at least to me) everyone sounds very similar when whispering.