How do I correct misspelled email name?

Whenever I send an email from my iPhone, it seems to autocorrect the spelling of my last name. I tried turning off autocorrect and turning phone off and then back on again, but it didn't fix the problem. I tried adding a signature line with my name, as someone suggested, and it did not correct the problem. I've been through all my settings to see if someone accidentally misspelled my name when setting the phone up, but my name appears correctly in every location that I can see.

I'm using Yahoo as my email server. This problems does not occur when I send out an email from my PC, only from my iPhone. Still, to be sure I've covered all the bases, I doublechecked the settings for Yahoo on my PC and can find no instance where my last name is misspelled.

This is a real problem when I send out business email. Any suggestions for how to fix this?