Customer details are not secure!

i'm having an issue with my opencart website,
i am taking orders on phones from some customers and they dont use any email services so i have to generate an invoice from my opencart store so i made their accounts and set the same password for all customer accounts i created and whenever the client open their account they have 2 addresses on their own and one address from any other customer's account.
i think its a huge issue so please provide solutions if you have any
thanks

Yep thats going wrong.
Had the same isseu.
created a workaround that is fast and easy to do.
make sure youre logged out of your admin and shop.

go to front of shop
create a account with all credentials from your customer.
make sure if they have a email adress like nlah@blah.com to make sure that you input it as blh@1blah.com that way your customer does not recieve a account creation email, use a password you can remember, i use the same password every time i create such a ccount for future orders.

next staying in that account add desired products.
when finished, go to paymants as needed but just dont pay.

logout.

go into admin.
oder can be found under abandedned orders,
modify order status and its visible.

process order as needed.

any other way? , because it will take extra time.