Two popular budget providers, but on different networks: Wingo (Swisscom subsidiary) on the Swisscom network, Digital Republic on the Sunrise network. Both focus on online self-service and low prices.
The choice mainly comes down to the network. Want the Swisscom network with the best rural coverage, take Wingo. If the Sunrise network is enough (equivalent in cities), Digital Republic often offers the more transparent package with fixed permanent prices and a free eSIM. Both are cancellable monthly. Compare the actual prices above, they are current.