courier not reached, no response from DTDC

Sir,
My DTDC courier tracking number is B23911837. The content inside was an iphone 4s(white) mobile phone. The courier’s status is showing in Muzaffarpur(Bihar) but they said they don’t have our parcel. I registered complaint on DTDC but i didn’t get any response.
Now they are not even picking up my phone call. I think they have stolen my phone. Please guide me what should i do next.
Thanks!
My email address – “[email protected]”
mob. no.- 09591413770