Harassment by Truworths account department

I have been a loyal customer of truworths for many many years and I pay my account each and every month. If there is something they should know, I phone them and make arrangements. I do not skip a month, I pay every single month, but recently my commission was cut at very short notice and I did not have time to inform Truworths accounts dept that I will only be able to pay a certain amount but will catch up. I pay my account on the 7th of each month, which I phoned them and arranged with them. I paid less then the installment on the 7th (at least I paid something) and on the 8th the phone calls started. I made an arrangement with the lady and explained my circumstances. They phoned again on the 9th, 10th and so on and so on. EVERY SINGLE DAY, I HAD TO EXPLAIN TO EVERY SINGLE NEW CALLER THE SITUATION, EVERY SINGLE DAY. They literally drove me insane, and many of them put the phone down in my ear. I am sooooooooo disappointed in their after service regarding accounts. If I was a customer that frequently did not pay my account, I could understand the harassments, but I am a loyal paying customer. Their harassment calls is horrifying, truly.