Invalid sim by telkom mobile

Telekom Mobile is the worst ... my SIM card continuously says invalid sim or sim failure every 5 minutes my device has to be turned on and off again it’s going to end up damaged and they will be liable for the device since I’ve called them several times they consult disconnect calls cause they know nothing and never even call back .... I demand this is fixed my number is+*** I can not go on like this my data will end up expiring.