Telkom
Not cancelling an account taking legal action

I cancelled a Telkom account 3 months ago already.
They keep sending me messages of legal action and warrants to sell assets to recover costs.
No first of all it is impossible to phone Telkom and get hold of the right person to correct this.
Also they have phoned me about this and I told them the account has been cancelled but they ignore this and continue sending legal action SMS's.