No storeowner would sell you an item on a credit card knowing that you intend to retun it. To buy from him with that intention without his knowledge is pure genavus daas. It is also genavas momon because you are causing him to lose 3% or more by “buying” and then returning. He is willing to absorb that loss for legitimate customers but not for genovim who are only looking for points.
As far as the credit company is concerned if you think their position is unclear call them and ask them. Let us know what they tell you.
Just becuase you go to Rabonim and leave out facts (ah ganev bleibt ah ganev…)doesnt mean everyone does.