Annoying inappropriate reminder messages

The SABC has been terrorising my mother for years now. Some how they both her and my number and have been sending messages for us to pay for a TV licence that does not belong to us.

My grandmother who was the account holder, passed on in 2012. We have advised the SABC of this and even faxed her death certificate yet they still send us messages to pay. I recently sent an email to them explaining this, no one contacted us and this morning I got another SMS.

We are sick and tired of this..