Mini bull terrier breeders bad service

They do it just for the love of money I bought a puppy that within 6 months was cripple due to deformations in his legs and had to be put out. Do not offer to replace him rather ask more money for a new one. Our children is in shatters as they were devastated an so looking to new friend but with this outrageous money that is asked of us to pay in we cannot afford. We already paid R18 000 and now additional R7000 is ask of us for a new one. :(