Pep Stores - Bad service and incorrect clothing sizing

Yesterday i bought a pack of two by size 16" short sleeve shirts.
Having bought shirts for roughly 30 years, i am well aware of my neck and collar size.
when i treid the shirt on at home , it was far too small and returned to your store at Pine Crest Centre.
an assistant then gave me a replacment shirt with a collar size 17" , which for all intents and purposes should be correct.
I was stunned by the attitude of the cashier who had the nerve to ask we who is going to buy this now? and then proceeded to make me wait while she repacked each shirt - GREAT CUSTOMER SERVICE.
To add insult to injury, i get home and try on the new size 17" shirt and believe it or not, this shirt is still too small!!
As i write this letter, i am sitting looking at a Signature 41 cm shirt which i bought from Edgard which fits me fine.
under normal circumstances, I would simply return it but after what i experiences today, i am dreading getting into a confrontation with your very unfriendly staff.
Please advise how i am to overcome this problem as well as how this bad service in your store at Shop 306 Pine Crest Centre will be addressed.