美版4S嚴重回音問題~&退貨詢問

[saku0911]

請教各位大大~
有人跟我一樣是用美版4S嗎?
4S 16G黑色 台灣大哥大
4S 16G白色 威寶

兩隻在打電話時都會有回音問題~清楚地聽到自己講話的聲音~發生機率約6成....
想請問是我哪裡設定錯了還是拿到機王嗎?
有沒有哪位大大可以分享一下使用經驗


另外請問如果要退貨的話~我的啟動日期是12/23
Your product is eligible for complimentary telephone technical support during the first 90 days.
Estimated Expiration Date: March 23, 2012
More about complimentary support
美國的4S是14天內可以退款還是30天內呢~感謝!!

[saku0911]

補充一下~兩台都是裸機使用~
也使用過→設定-一般-重置-重置所有設定，來跑過了~
問題依舊存在~麻煩各位指點一下~謝謝

[saku0911]

再推一下

iPhone Return Policy If you are not fully satisfied with your iPhone purchase, you can return your undamaged iPhone to the Apple Online Store within 30 calendar days from shipment for a full refund by calling 1-800-MY-APPLE. If you return your iPhone within 30 calendar days from shipment, you will not be charged a restocking fee. The iPhone must be returned in the original packaging, including any accessories, manuals, and documentation. For more details, refer to iPhone (http://store.apple.com/us/help/iphone#addinfo) Help page.

是指IPHONE系列30天內可以直接退貨嗎?
但請問他是指30天內退回到online store 還是30天內寄出~因為飛機的關係可能有點來不及~謝謝