Mobile phones & SIM
Even in Palestine (West Bank), mobile phones are considered a necessity.
You can buy SIM cards, or even also mobile phones inside Palestine.

Palestinian mobile network operators
There are two mobile network operators in West Bank.
JAWWAL
JAWWAL is Palestine origin, a long-established operator.

Roaming doesn’t work in Israel (checked in 2011). Call to Jawwal in Palestine is very cheap, also in Jordan through Jordanian networks.
Ooredoo (formar Wataniya)
Ooredoo is of Qatari origin, established in 2009 in Palestine. The brand was called Wataniya until 2014.

The price is a bit more costly than Jawwal.
A call would be cheaper between the same operator. Check in advance which operator is popular among your friends, then choose the one.
How to get a mobile phone & a sim card
There are many mobile phone shops everywhere. Tell them you want to buy a SIM (maybe with a phone). That’s it.

There are many types of phones. Even iPhones can be found (from 400 NIS for used ones), or the ones only with call and SMS from 100 NIS.
SIM itself costs about 10 NIS without a top-up.
Before going to a mobile shop, don’t forget your passport to buy a prepaid SIM.
How to top-up
Top-up is possible at mobile shops and grocery stores with Jawwal or Watania marks.
Tell the cashier you want a top-up with which operator and how much.
The minimum top-up amount is 10 NIS or 15 NIS.

In general, they sell Top-up prepaid cards. Get a PIN by scratching, then call the top-up number and press PIN.
But top-up calls might be difficult because it’s in Arabic. In that case, ask the cashier or your Palestinian friends a help.