Before you start

Unlocked handset
Passport or identity card for mandatory registration
Swiss address and bank account for postpaid contracts

Step-by-step

1
Get a prepaid SIM on arrival
Available in Migros and Coop and in operator shops around the station. Registration against your passport is a legal requirement — Switzerland does not sell anonymous SIMs.
In personWho: YouCommonly CHF 10–30 including credit
2
Compare the discount brands first
Wingo runs on Swisscom, Yallo on Sunrise, and M-Budget and Coop Mobile on the main networks too. Identical coverage at substantially lower prices, usually without a long tie-in.
OnlineWho: You
3
Check mountain coverage if you will be in the Oberland
Bern's canton runs from the Mittelland up into the Bernese Alps. Coverage in the city is excellent on all three networks; in the valleys above Interlaken it is not interchangeable, and Swisscom's rural reach is the usual reason people pay more.
OnlineWho: You
4
Move to postpaid once you have an address and a bank account
Contracts need both and sometimes a permit. Prepaid is the bridge.
OnlineWho: You
5
Add an EU allowance if you travel
Swiss plans differ enormously in what they include across the border, and the cheapest plan is rarely the cheapest once you add roaming.
OnlineWho: You

Documents you’ll need

Passport or identity card
Swiss address for postpaid
Swiss bank account for direct debit

Things most newcomers don’t know

EU roaming rules do not apply to Switzerland in either direction.

An EU SIM roams here at non-EU rates, and a Swiss SIM in Germany, France or Italy can be expensive unless the plan says otherwise. People who keep an EU number for a few months after moving are the ones who get the shocking bill.

Source: Switzerland's non-EU status under the roaming regulation

SIM registration against ID is compulsory and matters later.

A SIM registered in a colleague's or a landlord's name cannot easily be ported to a contract in yours, which is exactly what you will want to do three months in. Register it correctly on the first day.

Source: OFCOM — telecommunications regulation

Bern is the one large Swiss city with no accidental-roaming problem.

Basel and Geneva sit on national borders where a phone left on automatic selection registers on a foreign mast from inside a Swiss flat. Bern is deep in the Mittelland, so the network you pay for is the one you use. One less thing to configure.

Source: community-reported

Common mistakes to avoid

Assuming EU roam-like-at-home covers Switzerland.
Keeping an EU number after becoming a Swiss resident and paying roaming daily.
Signing a 24-month flagship contract without checking the discount brand on the same network.
Registering a SIM in someone else's name and being unable to port the number.

Some of this may be out of date. Spotted something inaccurate? Help us keep it right for the next newcomer.