Sorry to hear roaming is not working for you in Israel.
You can check roaming is active when you log into Your Account . Click on plans and devices then click the tab manage devices. Make sure roaming is set to on here.
If you're not able to pick up any network it maybe that roaming is not active on the account even though it may show the contrary. It may also be the case that the local carrier is not compatible with your handset.
I have included the help page showing call prices when using roaming in Israel here should you get this sorted.
If you wish to give the mobile team a call whilst abroad you would need to ring +447953967967 from a working line.