Wrong billing for over 5 months

Telkom keeps billing us for a wrong Fibre package and despite alerting them to this for about 5 months, they have failed to rectify the matter. As a result they have suspended our fibre connection even though all their Call Centre agents keep agreeing with the fact that the account being billed on us is wrong. They claim for the matter to be resolved we have to speak to their Sales division, which then must speak to the billing division and that one too must then refer the matter to the IT/connection division. Apparently all of this can't be solved through 1 call and it now appears that it can't be solved in 5 months either. What a sorry excuse of a company!!