Bad service

Hi I have been behind my installment and I had been switched off in September and I made an arrangement to pay my monthly installment on the 1st of each month which I did for October and I had made arrangements to pay the overdue amount of 1550 an installment on the 9th and yesterday made a payment of 793 towards my installment but they say it has gone towards my PtP amount but it's not the 9th yet and now they say my monthly installment is overdue for 1250 but I paid 793 and my next installment is on the 1st of December and I've been disconnected since this morning they keep saying they are looking into it