IPhone 4 straight talk issue?

I have an iPhone 4 brand new 5.1.1 OS and I have microphone problems when trying to call. I made a video and tested the microphone through there and worked perfectly

I've connected a headset to the phone and it still didn't work. The person on the other side doesn't hear me. I can hear them fine.

Anyone with straighttalk and iPhones that has this problem by any chance?

There are two potential issues here:

1.) A potential issue with the phone itself, which is not that likely, since you indicated that the tests you did came back satisfactory. I would not rule out a phone fault yet, though.

Where did the phone come from, and what carrier was it meant for?
I will revise my answer when this information is provided.

2.) The most likely issue is with Straight Talk itself. I would call them to see if there's anything they can do, although that is likely to be a pointless measure as the "Bring Your Own Device" SIM program is not meant for casual cell phone users, but for those with an advanced knowledge of how to modify their phone to work on their system.

There's more that I can add to the second part, but without the information about the carrier the iPhone 4 was meant for, it could get to be a tad confusing to fully express here.