Refuses to see reason

The first month that circumstances forced me to be unable to make my monthly payment, thry keep sending me threatening emails and WhatsApp messages, after I send several emails explaining my situation and confirming that I will make monthly payments till I'm up to date with the one payment missed, I just can't pay the amount they want by the date they want, but they refuse to see reason and refuse to accept my arrangement, they just dont want to help people