help please.. how do you kill rats?? traps and poison didnt work?

at the end of november my dog was acting up... going into the kitchen and going to the cupboard under the sink and crying and scratching it. after a day or so i thought ill empty it and see whats going on... there is no food in that cupboard its mainly my washing powder and stuff.... so i emptied it and found a bag of old dried dog biscuits... they had been chewed through the bag. there was also alot of bags chewed up. i have completely emptied the cupboard now and there are some traps in there and poison... but they remain untouched. the dog stopped acting up at the cupboard so i thought welllll iv scared them off.... then a couple of days later he started acting up in the hall way... trying to dig the floor up!! so i thought they must have got under the floor! so i noticed a small hole in the back of the cupboard which im assuming leads to under the floor.. so i dropped poison down there. the dog never stopped acting up but it wasnt as bad so i thought they must have all died but he can still smell them. so last night i went to put some rubbish in my wheely bin at the front door... opened my bin and there was a rat sitting in there! i screamed and it dived into my bin. once i had got over the shock i decided to look around... my bin is almost right against my house wall so i pulled it away and there was a small piece of wood... about 2ft long and maybe 10cm wide which was on the ground right against the house, i seen a sort of little tunnel going under this piece of wood so i moved it... and there is a tunnel going right under my house. iv put a trap near the entrance but they seam to be avoiding traps and poison.... so how else can i kill them? my mum had the same problem in her garden shed and she called the council and they put poison down and this was back in october but the problem remains. why are these rats not dying?