Line Cord Error on BT8500 and slow broadband

[#1]

We have been getting an intermittent line cord error on the BT8500 for some time and done the checks suggested (unplugged, cables all tight, etc) but don't have a second handset to test if it is the phone handsets.  Does anyone know what else we can try? No joy from Plusnet as can't get through to customer support 

[#2]

It looks like you've since contacted our support team and we've raised a fault through to Openreach

We'd expect an engineer to investigate within the next 48 hours