I would wash the panels, dry them, and then see just exactly what I'm working with.
If the design is printed off-grain, no amount of pulling, etc. will get it on-grain.
I would salvage what I could of it, and then rework it - if I still wanted to fight with it.
Have you considered returning it to the store?
I'm a fanatic about working with the grainlines running in the intended directions.