How do I get rid of Vodacom?

Inhave tried to stop my data contract with Vodacom since February this year. I spoke to numerous agents, I even sent emails. They stop it and then reinstate it again without permission. I am now at the point where I want to stop my other contract also and just have zero association with this place. I spoke to agents at customer services, cancellations, after-sales and retentions, even to managers. After almost 15 years with not even one missed payment, they cannot honour one request from me.