Payments not credited

I've been in and out of hospital since the beginning of the year. I made payment arrangements with Edgars and we agreed on an amount that I would be paying. I've been making the payments every month. Recently I've been receiving text messages saying that my account is in arrears. Today I got a call from the Call Centre and again after explaining the agreement that was made was told that the agreement that was made is completely irrelevant - I won't pretend I didn't lose it! These people are the WORST now my credit record is going to look like a shambles because your team doesn't communicate with each other. I cannot wait to close this account, no customer deserves to feel like a ******** because of your inefficiency!