Galaxy S5 SM-G900FD

I have Galaxy S5-SM-G900FD--Duos-Klte model. (UAE version)
Device is rooted.

I'm not able to use both the SIMS to make phone calls.

SIM-1--WCDMA / GSM mode---Can receive / make phone calls.
SIM-2--GSM mode--No audio while making / receiving phone calls.

On the Other hand,

SIM-1--GSM mode--No audio while making / receiving phone calls.
SIM-2--WCDMA / GSM mode--Can receive / make phone calls.

Dual SIM remain always on, even I tried to switch off and check no use.

Kindly help me in using both the SIMS for making and receiving phone calls.

Thanks in advance.

Samsung Galaxy S5 Duos (SM-G900FD) Custom rom

Hello,
I just Purchased samsung Galaxy S5 G900FD. I tried to install a custom rom (miui). Every thing works fine but its not registering to the networks. i tried flasing modems from stock roms but it didnt work with MIUI. Any Solution?
Thanks