Incorrect billing

I am a new customer. I approved their debit check but they failed to debit from their side. Sent me a note that I must pay R189, I paid. They kept on with the msgs until I called & told it takes a few days to reflect. Next msg said I owe R134.45 & the next one said R135. I called they said Ozow Pay Now is having a problem, it's not reflecting payments. Not to mention the phone calls I'm getting, when I answer they don't speak.