Unexperienced workers

I have 2 decors on my name. I have closed one in 2022. Last month when I made payment our dstv wasn't playing, I then called they allocated my payment on the decor which was closed a while ago. They then moved it to the one we are using. Now my service is disconnected when I call this morning they said I owe 500+ yet I have paid on the 3rd of October. They want me to pay for their mistake because we don't use the decoder they said I must pay. If have called several times this month about the same error where they have disconnected some channels. If I had to give multi choice 0 start. I would gladly do it.