go back to them and tell them that you wanted a quiet muffler and that you arent happy with the muffler that they have put on. a cannon will never be quiet, its not baffled. as sss said.. quiet = baffles.
if they dont sell lukey they will have other brands. my parents say beedhams are pretty good. dont go to toys muffler mart in redcliffe. they're pretty dodgy.
so yeh, go back, tell them that you asked for a quiet muffler, which they said they would do, and that they didnt deliver and you want your money back. dont take any shit from them.
try grahams exhaust (its a green shop) just a few doors down from jack beedhams on anzac avenue. my mum and dad have gotten exhaust work done by sr automotive in the past, but i'm guessing they just sent it back to somewhere like jack beedhams anyway.
either way go complain to them and tell them that they havent done what you asked and you at least want it changed over.