Q: activation iphone se

Ing general if your iPhone is locked by a carrier, you need to contact this carrier to unlock it. Note that this is only possible when the contract has been already terminated and there're no charges left to be paid. In your case the only way to do this is to contact the seller.

Which store?

IF it was CarPhoneWarehouse (perhaps others), it is not unlocked.

Take it to the place where you have purchased it and explain the situation.

Cousin Sandel wrote:

 

they sad that the phone is sim free. What I must do?

SIM  free does not equal unlocked. As Thunderzzz states above, contact the store where you purchased the phone.

You would need to contact CarPhoneWarehouse to determine their return policy.

Just because it's SIM free doesn't mean it's unlocked.  If you want to know if you can return it, ask the people you bought it from.