Can a dog build tolerance to the prong? What's your recommended action to resolve this? Should I work on my level of corrections when he pulls and use a higher level?

Hi- thanks so much for the great site, I currently am spending money with you guys and will continues to do so to support a great resource. I know you get tons of questions and I have read through hours of the site on multiple occasions. I have a just turned 2 year old GSD male, not perfectly trained by any means but I am working on it hard. I really want to get 1 thing under control and its the pulling on leash. My dog will come when called, stay forever, sit, down all that on command and every time, but some where I have failed on the not pulling on leash and staying by my side. I use a prong collar and have tried 3 different sizes of prongs because my dog always seems to pull straight on forward no matter, almost like he has built a tolerance. I am pretty sure they have been fitted properly I have them on tight and I apply them like you state on your site. Can a dog build tolerance to these? What would be your recommended action to help resolve,would this be to watch establishing the pack structure as this is a dominant dog issue? or just lack of training? Both? Should I work on my level of correction when he pulls and use a higher level? Any input would be appreciated, and should I use a fur saver instead of prong or is that only replacement for choke collars, thank again for any input and time you take to answer my questions, I assume this is all due to my failure to teach him properly.

Thanks Matt and Gunnar

I am trying to put an order together later tonight to ship out asap and will add some things you might recommend, so please let me know, thanks.