Why won't my landlines recieve incoming calls

I have just joined and managed this account for my 80 year old mother.  Since the Virgin engineers have been out 3 weeks ago approx, her phone has stopped accepting incoming calls.  

Ive reset the hub and contacted Virgin, they said 2 days ago they would escalate the issue and raise a ticket, Ive heard nothing since.

All I want is to know I can contact her as Im 30 miles away.

Kind regards 

Tommy