Back to the topic, either your leaflets are $hit (and i doubt that because they would have to be really bad to get that response) or they didnt get delivered (wich is more likely)
whoever you paid to deliver them knocked you.
Deliver 5000 yourself and record the response
you then know what to expect if your paying someone to deliver them, and if they dont get the same response sack them and try someone else.
Also experiment with different leaflets, this does make a difference
I have know got my response rate to, for every 5000 delivered i get around 15 decent jobs straight away (within a week)
and then a few more trickle through over the next couple weeks
so i end up with around 20 jobs at £100 each thats £2000 from every 5000 leaflets
ps. it has taken me the best part of a year and a lot of different designs, racking my brains for new ideas and a lot of walking the streets testing designs to achieve this
but iv got it down to a fine art now

with £1100 worth of work booked in next week