ip phone 7821 didn't response when i make call and returned back to main display ,also phone doesn't call digits i typed

[amralrazzaz]

dear 

 (ip phone 7821 didn't response when i make call and returned back to main display ,also phone doesn't call digits i typed)

i have 2900 router with cme and 25 seat license and cisco 4 port voice interface  fxo and i have 2 primacell devices with two sim cards connected to 2900 router 

problem is some time when trying to make a call internally or out side not response and the phone come back to main display , i tried to restart the primacell sim cards and its working fine before but now it didnt 

so whats the problem is ?

again i try to make any call no response and phone didnt typing the digits and go back to display main screen

thanks

regards