Vodacom Cancellation failure

I have on numerous occasions in the last 2 years attempted to cancel unused mobile numbers for mobile modems no longer in my possession. The only attempt by Vodacom to assist with the cancellation was for them to reduce the payment for these extra numbers. I have contacted Vodacom Customer Care (excellent service!) but have never been able to make contact with or talk to anyone from Cancellations Department. I am a pensioner and the additional R500 for unused items is financially nonviable, especially considering it has been continuous for 2 years. The assistance to renew or upgrade is obviously fantastic but any reduction or cancellation is met with a brick wall of silence.