Adding screen insurance to account

I recently upgraded my contract and found R79.99 screen insurance added to the account. I contacted them immediately and was told that it was a once off payment paid by Vodacom and was reflecting as a credit on my account. Screen insurance ***~JVPK. The monthly deduction did not include the monthly insurance amount so I gave no further thought. I have just received the next bill and the insurance is back on both accounts that I hold with vodacom. I did not authorise screen insurance. It is not part of my contract. Vodacom simply added it to the account and took the money with the next debit.