You don’t need to have the account holder with you but you do need to be listed on the account as an administrator.

So like i am the one who calls and deals with any issues that arise including billing, is that enough? 

So, you are an authorized person?

Even if you are an authorized person, I think it would be better if the account owner called Koodo ahead of time and told them you were going to a store to upgrade the phone. They can put a note about it on your account.

When the rep in store pulls up the account, your name needs to be present along with an administrator role. This is something that would’ve had to have been setup by the account holder at some point in time.

Like Mayumi said, you can have the account holder call in to double check this/leave a note/make the proper changes.