Shocked

I am absolutely appalled. They phone me then hang up after one ring or as soon as I answer they hang up. Do they then put in there report that they have tried to contact me without any luck. I have sent numerous emails but none have been responded to. This morning, 02 August 2019, I get an sms to say that my file is with the legal department and to avoid any further action, I have to pay before 13h00 on the 01 August 2019, or contact them via email or phone call. So, I am not understanding how I should make sure that I pay them on a expired date. I have phoned the person to contact on the sms, but they would not transfer my call. I have sent her numerous emails since last week, which she has not responded to. I really do not know which way to go, as I am desperately trying to pay this off, but am having no joy in dealing with them. I can't imagine that they get people to pay their debt with this work ethic. Always threatening, but never responding to correspondence.