Future flight credit conversion to ETC

Hello has anyone had luck with the process of converting from FFC to ETC ? I did the email thing and the First Lady agreed to do it but couldn’t locate the confirmation code so when I replied where it was the second worker denied to transfer it.. which is confusing because the first was willing to do so.. any luck? This is For united I have future credits but I want my sister to have mine so trying to figure out a work around. It’s not expiring for another year.