Telkom Options for blacklisting cellphone

My cousin has been trying to blacklist her phone for over a month, but can't get help because the person who stole her phone still uses her number and as such she doesn't have valid answers to the security questions. She can't submit a R4000 insurance claim because of this. Is there no way that she can get assistance. We spoke to an agent who said that we can't get help, but surely there must be a way.