Still didn't received my replacement phone

Replacement iPhone. I had contacted you last week regarding issues with my iPhone. The representative informed me that a new iPhone was warranted. I have yet to receive the new iPhone. I just received an email stating that I need to except a charge of $699 and I have two days left to do so? What am I supposed to do? Am I supposed to except those charges? They were replacing the defective phone. I need some help with this please

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