Go to settings > about device > system updates > check now. If it doesn't come up then your device probably can not support that version of Android.

According to this: https://www.frequencycheck.com/carrier-compatibility/ApjPHYG/samsung-sm-g930f-galaxy-s7-lte-a-samsung-hero/h2o-wireless-united-states it should work on most carriers.

I think something like this is what you are looking for. IPhone 6 plus earpiece http://www.amazon.com/Original-Earpiece-Speaker-Replacement-5-5inches/dp/B01B1KDZWM/ref=sr_1_4?ie=UTF8...-4&keywords=iPhone+6+Plus+replacement+spe...

If you are getting issues with your cellular service no connecting, follow these steps.

1) Turn off the phone.

2) Remove SIM card using tool.

3) Replace SIM card (just slides back in)

4) Turn phone back on.

If problem persists, try a hard reset. Then from there try a restore.

Anything past that is most likely a hardware issue. You may have broken a cable or damaged the board in some way.