It’s believed that NTL originally designed the system so players purposely don’t have their own personal zenni bank as a way to cap zenni, for economic reasons.
For now the only alternative that is suggested, is to do what players conducted back retail Dragon Ball Online which is if you want to store zeni in the bank then it’s best to create your own private guild.
This way you can use it as your own personal storage (as long as you do not recruit any players into the guild) for both in-game items and zeni.
Yea that's what I've been doing since retail but not all can do it. But thanks for the response