You can:
Send it back and get a smaller neck and tailor it
Or
You can tailor what you got...
Or
You can go with the old shirt style... and tailor it
Either way you go nothing is going to fit you. You can look like a slob as the company has set you up for or eat the 10-20 bucks to tailor each shirt so you don't look like a hobo.
Welcome to JetBlue