Landline Disconnected for no reason.

They just decided to cancel my Mom's landline, she is not owing anything, in fact she has R541 credit. I called to ask what the reason was behind the decision, was told they wanted to change her number to a new one. That shouldn't be a problem, inform us and do the right thing. My Mom has had this line for more than 20 years and she is pensioner. She went to Maponya for clarity and was told to apply for a cordless where she would be paying R270 monthly excluding calls, that is ridiculous!! She is depended on that phone, so Telkom wakes up one day and decides to cancel the line, that is unacceptable, unprofessional and insensitive. Can someone please explain, we don't want the refund but the line back please!