[US] Where or who would I report a scam like this to?

I work at a well known phone service retail store, in the past week I have had customers coming to me to activate a phone bought in the back area of this random food spot in town, combined with a "phone repair shop" They NEVER WORK. Some are reported lost/stolen, some check out perfectly, but they never work. Customers come with the same story saying they took their phone in for repair, repair "couldn't fix it too badly damaged" so they "replace" it with another phone they have in the store for them. Always an iPhone. they are left with a bootleg POS phone that doesn't work at all but looks perfectly fine and normal. Definitely some type of scam going on and cheating people out of phones and money. Where would I report something like this? The local police in the area likely would not do anything at all.