I've just been told the same thing by Customer Services (the individual I spoke with also went away to get advice). They can't take an LPA access code and only way to discuss my mother's account is to get her on the phone first. She's in a care home with dementia. From the earlier chain sounds like there is a process but Customer Services don't seem to know what it is.
this post is similar and the links mod posted may help
Thanks. Yes I’ll follow the instructions and hopefully that works. Seems odd that Customer Services don’t know this. It can’t be unusual.