Poor service delivery

I contacted sigma last year to advise I am unemployed and I would like to make a payment arrangement.I have been adhering to the arrangement.I sent emails to advise my phone is out of order and instead of paying on the 7th I will be paying on the last day of every month.I am getting assistance to make a small payment.I still to date receive no response to my emails and still receive messages stating there is no arrangement made.How is this possible when I have submitted the proof of payment through every month that I paid.Even though I have made payment I still receive messages to make payment again