Vodacom contract

Had a contract with Vodacom of which they were debiting an amount more than the amount we agreed on and I complained after 2years of the matter being not resolved but finally came here and the matter was resolved but now they have not canceled the contract even though I was told that after the last installment they will canceled and I just received an sms with an amount I'm Owing now. Kindly resolve the matter ASAP as this will affect my credit score