Hi Jov6
Very sorry to hear about all those issues you are having. It sounds like you have really been through the ringer with this one. It definitely sounds very much like you have a fault on that line likely caused by the storm, like you say I doubt it would be just congestion of something like that. Evidently you have already contacted our helpdesk. As it has been an ongoing and persistent issue I would get back to them and ask them to raise a complaint for this if this has not been done already. They can then get someone managing that who will chase it up on your behalf.
If you haven't had much luck with the engineers and if they are not finding an issue, it could potentially be what is called a REIN issue where there is electronic interference with the line. This is very rare but it is just a thought if so many engineers are havig no joy fixing that for you. Or it could be the cabinet perhaps and a lift and shift of the line could be required - those are both thing and engineer would need to pick up on though.
I wish I had something more helpful to advise you of, but all I can really do is urge you get back to the helpdesk so we can perservere with this one and hopefully get a resolution for you, as you have a business to run at the end of the day!
I hope you can get this all sorted ASAP!
Regards
Ryan