Account not sorted out after 2 weeks

Vodacom debited my bank account for my cellphone contract but for some reason it was rejected. I did pay my account with cash the next day but they said I still owe them R100 for the rejected debit order. They then said I must send them a bank statement showing proof that I did have enough money in my account, which I did on the 2nd of November. My account has still not been sorted out after many attempts to do it myself.