Cannot create account in app

I have been trying to create an account for my sister in law for her new VM account since 30th January.

I firstly got virginmedia.com e mail address knocked back so got a new address.(mail.com) which was accepted and then no matter what I put in for a password I got that knocked back. When asked for name and account no got the message account not recognised 

Tried VM on WhatsApp and they tell me account is showing ok and services ok which they are.

Because of this she cannot set up a DD for payment and e billing etc. She has regularly been talking to reps on phones and getting nowhere. She has an issue with the contract because it's a higher value than offered on phones.Need to have correct account value before she wii accept contract.

She has just had a helpful person on WhatsApp who tried to help and gave us the dummies guide to creating account in app. Tried 2 phones and a tablet,even clearing cache and deleting app and reinstalled but cannot get past the error.

Would appreciate any help or advice before she chucks towel in and goes elsewhere.