Eastgate Debonairs bad service

Around August last year my mom and I ordered a pizza at the Eastgate Mall Debonairs. Firstly, the order was incorrect, secondly the box it was served with was dirty. We returned the pizza noting the incorrect order and the dirty package that it came with. After some waiting we received the correct order on a new box. Initially they had removed the incorrect order and put the correct order in the same box, we insisted on a new (clean) pizza box. The manager apologised and said that the next time we come for an order we should come to him and he would give us a free pizza. This past saturday (13 January 2017), my mom and I went back to the Eastgate Debonairs, placed an order and tried to claim the free pizza that was promised to us. The lady that took our order is the same one that had served us the last time, she remembered us and phoned the manager to inform him of the promise that was made to us (the free pizza). A new manager came to meet us, he acknowledged that this lady that took our order related our previous experience to him, but because that manager that had promised us the free pizza has left, we can't have the free pizza. He said that that guy is not around to verify the story, surely that is irrelevant because the lady that took our order was witness to our last visit (she's the one who even told him the story before he met us). When my mom mentioned that to him, he then said the previous incident was in August last year. Is there a deadline for claiming promises made to customers to make good on bad service? Not even a year had passed and he says August was a while ago. I am expressing my utter dissatisfaction with the treatment that we received at the Eastgate Debonairs. Even when my mom was talking to the new manager, the staff in the background was giggling about the matter. In addition to how they treated us, while we were there on Saturday, one customer complained that her order was wrong, another customer complained that she'd been calling for a while and no one was picking up, when she said that, the lady that was taking her order said that the phone is on silent "askisi". Eastgate Debonairs should improve their currently poor customer service.