Gnarly filament: just one of those things, or grounds for complaint?
Sorry to say it, but MOST wrap-unders are caused by end-users releasing the free end of the filament when handling the spool. It is mathematically impossible to introduce a knot during initial spooling, and all the reputable filament vendors these days have pretty careful free-end control when the spool is taken off the spooler and sent to packaging.

Where you may get knots straight from the filament vendor is if they're respooling very carelessly and let go of the free end. You should only see this with very cheap filament. 

So, it's possible that your vendor messed up, but you should probably rule out your own handling practices first. It's not hard to prevent losing the free end. The nicer spool styles these days have holes on the side-flanges for securing the free end during handling/storage. Or you can print one of many, many filament clip designs from Thingiverse or your favorite model site. 

If you're very careful with handling and still get knots, switch suppliers. Anyone sloppy enough to repeatedly mis-handle new spools is likely also using extremely cheap material, and there have been a lot of anecdotal reports of very nasty industrial chemicals being mixed into the colorants of low-cost filament.