Forced to pay my late fathers Dept By Direct Axis

I have been in contact with Direct Axis since last year after the passing of my father in July 2021. They contacted me with regards to the personal loan over R80k which (he) my father had with them, I explained that the person you are looking for is no more, they demanded a proof of death certificate, which I sent via email with all the details. till today I am still getting SMS's, calls, and emails from Direct Axis that I owe them, I always have to explain to them that the person you are looking for is dead please stop harassing me by calling and sending me SMS's but still nothing has changed. I lost my wife early this year because of this, she thought I had debts on the side that I was not telling her about. I tried to stop this for over a year now with no luck, please can someone help me.