Just a few mistakes
info => information 邮件中最好不要用缩写
But => However
what features do you want => what features you want
maybe => so that (个人意见)
include it => include them
Hello, XXXXX
Thanks for your message. We haven't found your purchase information in our database, it will not charge you any fee if you haven't purchased it. However, if you have purchased our product, please let us know and we'll give you a refund.
By the way, could you please tell us what features you want so that we could include them in the future version.
Sincerely,
XXXXXXXX