Vodacom - R3 data refill not deactivating

I am on Vodacom prepaid. Every time my data runs out, I automatically get R 3 data refill. I have opted out and deactivated this service so many times but I still get the R3 data refill every time my data runs out. I have contacted Vodacom's customer care service but they only told me to dial *135#, after I told them it doesn't work and that they should cancel the service for me but I have not received any assistance. Please cancel the data refill service immediately.