Have tried dialing *228, its for activation of mobile number and it didnt help.
Could this be due to fact that my post paid sim is 4 yrs old OMH? was using in samsung SGH-i559
But i see that lot of people are facing this issue and could be a software issue with HTC.
Spoke to HTC cust care at length and they said that there is small patch release in feb 14 which should resolve this issue. also they said that 4.4 release will happen in feb14.
Keeping my fingers crossed for this patch.