Marumo left it until late to break the deadlock and claim victory as the match appeared to be headed for a draw at Lucas Moripe Stadium.
Diminutive attacker Monde 'Messi' Mphambaniso rose from the bench to grab the all-important goal that sank hosts Pretoria Callies in stoppage time.
Daniel Msendami sent in a powerful shot that was parried by Callies goalkeeper King Ndlovu into the path of Mphambaniso who pounced and had separated the two sides.
Earlier on in the match, Bahlabane ba Ntwa were reduced to 10 men when Siyabulela Shai was red-carded but they managed to defy their numerical disadvantage to claim a 1-0 win and became the first team to qualify for the Nedbank Cup Last-16.