Telephone service cancelled worngfully

On 31 May I cancelled my elderly mother's ADSL/internet on her landline, using the Telkom website - no other option. I selected ADSL/internet under the options. Received confirmation by SMS, giving me two reference numbers, one for INT (internet) plus one for the landline number. I then received 13 SMSs throughout the night, every hour, to confirm. On 2 June I called Telkom from my mother's landline, explained to the agent I spoke to that under no circumstances must my mother's phone line be cancelled. She doesn't use a cellphone, so it's her only outside connection. I gave her both the reference numbers and she assured me that the phone line would not be cancelled. I was not given a reference number for that call, but the agent gave me her name. Lo and behold, yesterday my mother's phone line as cut off. Where does one go to in a case like this? The service is useless, and will my mother get to keep her old number? Unbelievable that a state-owned public entity can be in a position to deliver such a non-service!