There could be many reasons your phone doesn't work. The problem could be with the phone or the sim card.

Note: A good way of determining if the problem is the phone or the sim card would be to switch sim cards with a friend (who has a working phone) and try them. 

Step #1 in all troubleshooting is to refresh the handset connection by turning it OFF and then back ON

Then check if your phone is giving you an error message.
A few examples are: No Sim, No Service, Emergency calls only

In these cases, you want to make sure the sim card is in the correct way and that the sim card is active. It may help to take out the sim, put it back in and restart the phone.

To find out if the sim card is active:
For a Cellular Israel plan
You could call us: USA (718) 289-0195. Israel 072-224-3300
or email us at [email protected]
You will need to provide us with a phone number to cancel, order number or email address associated with the order.

For other providers
Call their customer service agents (usually speak Hebrew)
You could find other provider's contact info here.

If there are no error messages, make sure that there are full network bars on the screen because weak signals are a cause for the calls not going through.

Also, check your call barring settings to see if calls are being blocked. Make sure it is set on inactive.

A payment issue is a common reason your phone may suddenly stop working. When your payment doesn't go through the line gets frozen. To resolve this see here.

If the call goes through but no one could hear you or you can't hear them, you may have a broken mic or speaker.

You could bring the phone in and we will have it fixed for you.