Exceptionally dissatisfied

Telkom is the worst company I have ever dealt with, my Dad who is an elderly man was given a cordless phone by Telkom at the beginning of October, till today the phone has the same error - Invalid Sim - Failed to register Sim, he has sent many emails, made many phone calls and two visits to a Telkom store pleading with the Telkom on every occasion to please sort out his landline as my dad and mum require a landline......well done to Telkom nothing got done about it, I had visited in beginning of November and he told me about this situation, I went with him to a Telkom store and the response was we must call technical support or email technical support. I have tried many many times to resolve this and I am so frustrated with Telkom and their ****py service, they have done absolutely nothing to resolve this issue, you get pushed from sales to technical support back to sales and cycle continues. A spoke to many people and its always the same within 72 hours it will be resolved. I asked one of the call center agents, what would you do in a situation like this......the response ' i would cancel the service' , one of the agents copied me in an email which was sent to ********** and no response since the 8th of December. Telkom your service is ****! It has been 2 months and Telkom cannot solve this, what gives Telkom the right to do this? Do we as PAYING customers continue to take your pathetic service?