MTN bad service

I need your help been struggling to access your online portal that's why I'm here,I have been struggling with MTN South Africa it seems like they really don't care about my complaints please help,you my only hope it's been 3 months with no action ,they fail constantly to update my account at the Credit beareau and it affects my credit negatively it still says default and I pay my account every month without fail,I called,sent emails to their legal nothing is happening.