I'm sorry to hear that you've been unable to get the home phone service added back onto your mum's account. I'm afraid we cannot changes packages on here but have you tried calling us on 0345 454 1111 or texting us on 0753 305 1809 to get it added?
If your mum is the account holder, she will be asked to pass security first but after that, there shouldn't be a problem adding it. The system may ask to contact us if it sees that there is something on the account that may require a call. For example, a bundle, or to clarify something.
Regards,
Lisa