Mtn staff at Grove mall n customer care are useless

I was advised by email by mtn to return router to an mtn store 5 days before my do date. I returned the device last Tues 24 nov. The lady took over 45 min to do paperwork and finally said "ok goodbye. The device will be picked up later in the week". She further stated my acc is in credit. Since then mtn customer service staff have repeatedly and ********ly badgered me to provide an ID number, account no and insist i contact the store directly to follow up. I was not given any no or paper from the store yet mtn staff insist i have received such! To date I do not know if my acc was closed as mtn now says i owe them R800. When my package was 269. Useless company, useless staff, ******* home internet.