VODACOM CHARGING ODD AMOUNTS

I've been with Vodacom for many years. My contract was recently transferred to my employer since it now falls within my employment benefits. I paid my full instalment in May whereafter my employer paid the next instalment in full in June. Ever since my contract was transferred, I've been receiving calls & sms's from Vodacom's attorneys being HP Attorneys, which states that my account is in arrears. The amount that they now allege is in arrears is not even close to my instalment and it was charged to my personal name after my account has been transferred. I'm not even a client of them anymore but yet they charge me some odd amount. Being a practicing attorney myself, I contacted the attorneys to ask what the amount was charged for, but despite various requests and e-mails they don't even respond. I then went to Vodacom again to ask them what the amount was charged for but they could not even answer that. I'm fed-up. If I owe money then I will gladly pay, but no one can even explain to me why that odd amount was charged to my account. It is absolutely unacceptable that nobody can provide me with an answer but my credit record is now affected for absolutely no reason.