Bad service for whe two mnth and a week

So month of June the 14th went into the store to buy 9kg cylinder when I got to the department a sales man tells me they dnt hv it,I settle for the 7kg because of the loadshedding so I paid to evn fill it with gas,as we go outside to fill I see the 9kg but I'm like I want this one initially, so the guy just open a gastank filler he stops and ask security if we can sto so i can refund the 7kg so I can get 9kg he had just open the gas filler to pump ,security says no continue we can take the air out,so wen I go to refunds they tell me they can't refund as it's been filled , I ask can u pls keep it when another client wants it gv them this one call me to add the money get wat I want. They tell me it's hazardous they can't, I'm sick from the doctor can't fight this now leave the cylinder with my receipt in the store wrote my numbersin the back ,no call nothing 2 mnth later I follow up with customer service guess what my cylinder they can't find it anywer probably staff helped themselves to it. Im told to come get refund no sorry for not getting in contact with u not evn a 100 voucher to apologies 2 full month without my goods no communication just refund they are still investigating what a poor customer service.