On-going Technical Fault - Going on for Months

Hi, My 76 Mother is having a bit of a nightmare at the moment with her line. This has been on on-going fault for about 4 months now. With her line working then not working, and now it's completely not able to receive calls. She can dial out, but if you ring her, then there is a digital noise and it cuts out with a beep. She has had 2 Engineers actually arrive at the house on previous occasions and on both they blamed a fault outside of her house. One said it was at the box and the other blamed a neighbours connectivity. We have tested all the internal connections, and the fault remains with known working telephone equipment, so as per the engineers that were on site, it's an outside issue. She has not been able to receive calls for over a week now, which is a major concern as she lives alone at 76 and besides her mobile, no-one, including armed response, etc can call her landline. Customer services have been helpful on the last call we made (end of last week) but the call still remains open. The fault reference (lastest one) is: 375CWZ2809I5. Home line: ***. Account name: Heather Robinson .Your assistance in helping an elderly lady would be greatly appreciated.