change username and password of sysadmin user for BPC 10 SP11

Hello BPC gurus,

We installed BPC 10 SP11 for a client, now to comply with some regulations client wants to change the following

- Sysadmin username and password

- BPCAdmin username and password

- BPCUser username and password.

I understand that server manager --> Reset login credentials lets you change the password for sysadmin and the other accounts,

but is there any way we can change sysadmin account (service account used for installation)?

Thanks,

Maitreyee