Hi,
So you should have a trash icon in the HikaShop mail listing (in the backend).
First, I will recommend you to open the mail and make a copy of his content in a file in your computer. It will be your backup.
After that, you will use the trash icon in order to remove your override.
At this moment, your modifications will be removed and the original email will be use.
You will have the new design with the new content and the new improvements.
If you still have troubles for the bank transfer data in this email. Please tell us and we will see how to fix it.
Working on the official mail will be easier for us and will help all HikaShop users in the same time.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.