have you just had the dog,? as at 18 month old it should have been sorted out when it was pup (5-10) months. What i use is a norm rope lead, put on as norm with the loop to the left. When they pull, yank them back (hard) it will stop them on prob, because loop is right under throat, and it will choke them. Ive done it with 10st bullmastiffs and bigger dogs it stop them dead in there tracks . Tod my bullx grey will walk great on the lead when not working, but lamping will pull your feckin arm off. And after a while when i get pissed of with, i put rope lead and it calm him down a bit lol, but