Apparent bullying and harassment

My mom is a pensioner and has been paying these attorneys for a FNB credit card from the time when she was working. We pay R50 every month as per the agreement which I help my mom with. The dec payment was made late because of people going on leave over the festive season. She received a summons today and was threatened they will attach the house that she jointly owns but only owns on paper also going way back and was to help my sister get the bond. I can’t even remember when this debt was established it is so long ago. Is this legal that when she has been paying monthly they can now suddenly issue a summons and keep threatening her as last month she received a final demand which she had to go fetch from the post office as well and I emailed them about it but they didn’t bother to respond. Surely this is now apparent harassment ????, And bullying ??? Does anyone know what recourse we have and can they attach the house for a R27k debt if she is not the full owner and if she has been paying monthly what she can afford? Can anyone help please? Thank you