Cannot make or receive call iphone 6s ios 9.1

I'd bought my iphone 2days ago. Yesterday, after upgrade to ios 9.1 my iphone 6s have problem:

cannot make or receive call on 4g lte signal

If switch to 2g signal, it can make or receive call

What i have done;:

Reset network setting

restart

configured date and time

turning on and off my caller id

switch on and off then on again airplane mode

switch 2g signal to 4g lte, repeat

go to provider and change new lte sim card

change sim card to another provider

place my sim card on other phone, (iphone 6 and it works on ios 8 )

place other simcard in my iphone

go to apple service center(it says maybe ios9.1 or IC in signal port)

All that what i've done not worked and make me frustrated. Does anyone have some problem??

if yes, what have you do?

please help me

i am very frustrated about this,

thank you so much