yallo is the mobile offer that you can use to call your family and friends all over the world for the same bargain price as if they were in Switzerland:
The starter pack including a SIM card costs CHF 20.00 online and at retail point of sales with CHF 20.00 calling time credit. Or even better, just ask your nearest ESN-Advisor regarding your free voucher for a CHF 5.00 yallo SIM-card, redeemable at over 80 Sunrise centers Swiss-wide.
By the way: You don't need a new mobile phone for yallo. Simply use the yallo SIM card with your previous mobile phone (except for SIM-locked phones) and benefit from the unique price plan.