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 at the airport, in Migros and Coop and in operator shops. Registration against your passport is a legal requirement.
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
Lock the network manually if you live near the border
In Kleinhüningen, Riehen, Bettingen and along the Birs a German or French mast is often the strongest signal. Disabling automatic network selection stops a domestic call becoming a roaming charge.
Mobile appWho: 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
Pick a plan that explicitly covers the EU if you cross regularly
Almost everyone in Basel does. EU data allowances on Swiss plans vary widely, 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

Accidental roaming onto German and French networks is the classic Basel phone bill.

The canton is surrounded on two sides by other countries and the built-up area is continuous across all three. A phone on automatic selection will happily register on a German mast while you sit in a Swiss flat, and everything you do then bills as roaming. Lock the network and check what it has actually connected to.

Source: community-reported, consistently

Emergency calls near the border can reach the wrong country's dispatcher.

112 works across all three countries, but which control room answers depends on which network your phone is on at that moment. If you are calling from a Swiss address on a German mast, say where you are immediately and be explicit that you are in Switzerland. It costs seconds that matter.

Source: Cross-border emergency call handling

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 or France can be expensive unless the plan says otherwise. People who keep a German 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.

Switzerland does not sell anonymous prepaid SIMs. A SIM registered in a colleague'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

Common mistakes to avoid

Leaving automatic network selection on and roaming from your own flat.
Assuming EU roam-like-at-home covers Switzerland.
Keeping a German 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.