Unresolved Telkom case

I have received rude calls from Telkom's thrid party debt collectors telling that i am owing Telkom R20134.35 on an apparent contract i took with them in 2016 . Walked in a Telkom store they verified the contract but couldn't issue me the actual contract document signed and copies of my FICA documents given when account is opened nor the name of the store where this contract was issued i was given a Telkom ***** line which when i call it gets transferred to a call center and the call centre agents gave me another number which gets rerouted to the call centre again .I need this to be resolved urgently .I don't want my name to be blacklisted because of a ***** case that Telkom can not resolve for such a big organisation i am disappointed in their service .