Apologies for the late reply, I have been off for the last few days. I am so sorry that your mum did not receive a call from us, please apologise on our behalf that this was not done.
Looking at your mums account again this morning for you, I can see that your mum has already registered for an online account a few years ago, this is where the issues may be coming in.
I cannot confirm what email address was registered, however you can click on the forgotten email/password link which will prompt you to enter your mums details.
This should theoretically, let you reset the password, and once you're in your mum's account change the email address if required.
Please can you try this and let us know how you get on?
Kind regards Jodi.