They do not respond to emails

I've received multiple messages regarding overdue credit payment, but after sending multiple emails to various email addresses associated with the company over the past month to sort out the matter, I have yet to receive a response. However, they're apparently still efficient at sending threatening messages to me about needing to make a payment before they take further action, even though I currently have money in my account that is enough to cover the overdue payment but it's just not coming off as a debit order (the matter which I want to sort out). I currently live and work overseas so it's not easy for me to try phone them and I was hoping to communicate with them via email.. apparently that's not something they do.