LG G Stylo in call sound muffled / also kdz file > LG flash tool GSM ?

Hey guys

Have the T Mobile Stylo, rooted with TWRP recovery running 5.1.1

The sound when in a call is muffled, its just not clear, like no high tones at all
I'm asking people to speak up just to hear them, and yes in call volume is all the way up.

1 does anyone else have this issue
2 I have the T Mobile 5.1.1 kdz file, will lg flash tool put the phone back to stock with factory recovery.
3 LG flash tool showed cdma, this phone is GSM, is there a different lg flash tool for GSM ?

I am still have a few days to exchange, or return the phone.

Thanks
Mods please move if I am in wrong forum