Ruining credit records....when not debtors fault

Contract was cancelled in 2014 and number ported to another service provider, months later a statement is sent stating amounts owing. Contacted vodacom and advised contract was cancelled and number ported, told everything will get sorted.....what a joke....never sorted, statements continued being sent till R20k "owed" debt is then sold to debt collectors, even with legal assistance this matter is still not resolved, 6 years and this affects credit scoring and ability to apply for real credit, like bonds and vehicle finance..........is anyone willing to sort this out once and for all???????????