I use 018 and have been very happy with the quality of the calls and
the incredibly low price of 12 agurot a minute (I pay in increments
of 50 NIS up front, otherwise it's more expensive). No monthly fees,
1 second rounding (as far as I can tell) and the prepaid funds do not
expire. In the 6 months or so that I've been using them I have found
no catches at all!