Cell c contracts [ poor service and their agents]

Cell c and their agents have poor services. I was paying my cell c account to shapiro shaik n now to credit service solutions [css] n they tell me that they don't see any payments on my account. I sent them emails and whatsapp with proof of payment [ statement from shapiro shaik], but no response. My account is affected each and every day. They call every day telling me same story that I owe so much but they don't do any follow up on my account. Be careful of contracts.