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This is usually caused by the headphone jack thinking that a headset is plugged in. Try taking a headset or headphones and carefully insert and remove the headphone jack from the port a few times.
Try making another call.
i just thought about something, they took my sim card out and put it in another phone. i dont thing i will be able to check this, what do you think will it work without the sim card just to check it out.
If you are able to make calls with the speaker on, it's not the SIM card.
Please try what I suggested.
i will go back to att and have them reasign my sim card for this phone.
As I said, it is not your SIM card if you are able to make phone calls using the speaker. Try taking a headset or headphones and carefully insert and remove the headphone jack from the port a few times.