Harassment

I understand that I owe Truworths money, I haven't been on their bad payments books since recently when I lost my job. I am trying by all means to keep on paying my installment but I can't reach the minimum required money, so I pay what I can afford, atleast I am paying something rather than not paying at all. I was called by some Truworths debt collector asking that I pay the required amount, I explained that I can't afford that at the moment, this collector then told me that they are going to keep on calling until I pay the required amount and their calls are charged. I am already having a problem of finishing my debt and finding a job, but you are charging these endless harassment calls, I get calls every hour from the time I wake up. This is too much, it's not like I am not paying Truworths anything.