There are three major mobile phone providers: Swisscom, Sunrise and Salt. Then there are several service providers which operate on the networks of these three. To name a few of these providers: Lycamobile, Aldi mobile, Migros Budget Mobile, Coop Mobile and Yallo.
Normally, the offers of these service providers are cheaper than of the three big providers.
Getting a prepaid plan gives you more flexibility comparing to a subscription plan. Prepaid offers don't have a contract period and they often offer a cheaper deal.
However, the offers constantly change and it is difficult to recommend a plan which best fits your needs. On comparis.ch (en), dschungelkompass.ch (de), handy-abovergleich.ch (de) you can get an overview of all the different prepaid offers and contracts.