iPhone 7 plus Product Red call quality issues
I have recently purchased an iPhone 7 plus product red model and have been having issues with call quality. There are interjections of odd screeching sounds almost like the phone is under water when it hasn't even come into contact with water. My iOS is 10.2.1 and the model I have is 128gb. Phone was only purchased 5 days ago.
Is this a handset issue or a sim issue - how should I go about resolving it??
iPhone 7 Plus, iOS 10.2.1, In-call Sound Issues