Someone not doing their job.

Good morning. My Woolworths account was handed over to MBD Credit Solutions (Pty) Ltd, I have made arrangements with them to pay in 3 payments, end of Oct i made my first payment, if i may add more then i should have. Not even a week after i made my first payment i received a letter from them via email stating i did not honor my agreement etc. About every second day i have been receiving these kind of emails. Obviously I still need to still pay end of this month and next month. Can someone in your accounts please do their work as this is making me frustrated!!! And best of all is the lady i spoke to when i told her the other lady told me to pay R272 and this lady told me to pay R211 so i asked the lady what is the correct amount and she told me owh then you can pay R272, i asked her straight where the money is going that she tells me to pay more then R50???