Password Greenby and plusnet

[#1]

I am trying to make my account more secure as the password is quite old. Currently, I have the same password for Greenby and Plusnet accounts, i.e., I haven't changed either yet. 

Are they two separate entities now? 

Do I need to change the password on both or just one? 

I have never had an email to say the migration is complete, just kind of assumed it is. 

[#2]

I'm also a Plusnet customer.

We are in a half way house, the migration of SMTP server relay.plus.net to Greenby has yet to occur.

So I am not changing any working passwords unless the situation is forced on us.