Vodacom contract

I have had a contract with vodacom since 1996. Last year 2020 in March 2020 I lost my job as a result of the corona pandemic. I was not even paid that month. Since then I have been trying to uphold the payment. I have asked them to cancel the 1 GIG recurring data to try and get the balance up to date. According to vodacom the account is in "arrears" to the amount of R320! Because of this they cannot cancel the data, I told them nothing is set in stone. They are not interested in helping me, they just insist the account is in arrears and I must call the collections department. My husband and I only receive a small pension and cannot afford to pay more than the R500 that we pay each month. Please help to resolve this problem