Can anyone tell me where i can get advise and complain about a certain motorbike shop in dublin Ireland?

Bought a motorbke from a bike dealership in dublin and he told me he mislaid the log book.after a week i droped into him about it and he told me he cant find it and would apply for a new one.So far i have rang the motor taxation offices three times in in four months and the bike is still registered in the last owners name.what can i do.