G900T call problem

i have G900T galaxy s5 with call problem

phone gives full signal and network name in notification center but when i try

to call it starts dialing and keeps dialing for almost 2-3 minutes but dont

make call,

i wrote default efs with BST dongle and changed many super imei

but problem is still there,

sometimes it gives not registered on network then i repaired network, signal

comes but can’t make call,

wrote QCN but problem is still like that,

any solution..?