exchange question. .?

[jocampo86]

ok I bought my evo on Friday..and I am having issues with my earpiece speaker sounds like itssbusted ,so I called best buy they said they will exchange it,but I opened another new lin to get the evo, so I gave cousing my hero with the new line ,he lives out of state, so I swapped the evo to my existing account,ao if I go to best buy and they see that my evo is under my primary line instead of the new one,will tey still exchange it,??o do I have to ask my cousing to bring the phone and swap phones than go to best buy?they are within same family account...plese help