I just took on a new customer that has an item on the their phone bill for "OL STOP" at $100 a month including cable mileage totaling $99/month. They have not used it for twenty years and I suspect that the LEC has not even been capable of providing the service for many years. Has anyone ever heard of getting a refund from the carrier for such a charge? It may add up to $20,000 +

I, for one, would be very interested to learn what OL STOP even is!

I would suggest having the customer open a case with the Commission for Complaints for Telecom-television Services (CCTS) https://www.ccts-cprst.ca/ - they are often VERY effective at getting the Telco's attention and a quick resolution.

OL (overline) stop was used for very early key systems to stop multi-lines (overlines in Bell parlance) form hunting when an answering machine was in use after hours. The customer leased a cable pair from the carrier that controlled the feature and connected a simple rocker/toggle/SPST switch to it, and when the switch was thrown, calls to the main number would busy out when line 1 as in use. It became obsolete after voicemail came into common usage.

No kidding! I see the application but can definitely say that I never ran into it during my career in B.C.

I would speculate CCTS can help get that refunded, at least in part.