Are they too long for your feet. If so i'd really take them back but if you're convinced that they're not going to give you trouble I'd recommend a brand called Sorbolite.

I think they're made out of sorbothane or something but they're guaranteed to reduce impact by a fairly significant amount. I use them and like them.

More importantly if you don't need a large arch support avoid these since they'll give you blisters over the short term and more severe issues after a little while.

It's a bit of a gamble though honestly. If it's not an international trip I'd go back and swap them or maybe go to another local store from the same chain and see if they'll let you swap them?