Invalid prepaid voucher

On the 21/08/2017 I bought a Telkom prepaid land telephone( ********** ) voucher via the Internet. I tried loading the voucher on the phone but it kept on telling me that the voucher pin was invalid. On the 23/08/2017 I phoned Telkom on 10210 and spoke to a Sizwe who said someone would come back to me to my disappointment no one did. On the 24/08/2017 I phoned again and spoke to a Sarah, I had to explain my story again, she then said she would refer it to her manager Hosia who also didn't phone me back. On the 25/08/2017 I phoned once again and I spoke to Nandi, who I asked to speak to Hosia who refused to transfer the call, eventually she did transfer the call as I was upset. I spoke to Hosia who told me that the query was escalated to Voucher management and that he would come back to me the same day, up until today no one has bothered to contact me. What kind of a manager and staff is this that say they will come to you and they don't and how many more people must I speak to, to get my query resolved. The voucher I am trying to load is for my mother who is an elderly sick person who is at home the whole day and needs the phone.