At the lake, your phone switches to the Swiss network. You don't notice.
Swiss mobile masts stand right on the south shore, and their signal carries across the water to Germany and Austria. Your phone picks the strongest network, and then international roaming applies.
Even a little data adds up
If you use your phone casually at the shore, you quickly pay double figures in the Swiss network without a travel option.
Example with €0.24 per MB (Aldi Talk without a travel option, as of 8 Oct 2026). Your plan may differ.
- €0.24per megabyte of data, Aldi Talk without a travel option (alditalk.de)
- almost €3per minute for calls according to the Consumer Advice Centre of Baden-Württemberg, in individual cases bills in the five-figure range (Wochenblatt, 5 July 2026)
- Telekomas the only one of the three network operators without a surcharge in Switzerland, for contract customers (inside-digital)
Three solutions that each work on their own
You don't need all of them. Each option has steps for Android (with screenshots) and iPhone.
Switch off data roaming
Your phone no longer uses mobile data in the Swiss network. That is enough if you only want to save data there. Calls and SMS can still cost money.
To the instructionsFix your network
You choose your German network yourself. Your phone then does not switch in the first place, not even for calls and SMS.
To the instructionsSwiss data pack with Data Saver
If you have booked a Swiss option, Data Saver helps stretch the small allowance.
To the instructionsThe most convenient solution is a plan that already includes Switzerland. Compare plans
How close is Switzerland to you?
Every place has a detail map with all Swiss sites nearby and an assessment with sources.
Places where this happens
Photos from the region. Below each one: the distance to the nearest Swiss mobile site.
Photos: Christoph Langner
In brief
Do I have to have crossed the border?
No. A walk along the lake shore is enough if your phone receives the Swiss signal most strongly there.
Will I notice?
Often not. Some phones show only a brief message, and the bill arrives later. A look at the status bar helps: if it says Swisscom, Sunrise or Salt, you are on the Swiss network.
Does airplane mode help?
For a moment, yes. Afterwards your phone looks for the strongest network again. Only the settings help permanently.
Does this also apply in Austria?
Austria is part of EU roaming. It only becomes expensive if your phone picks up a Swiss network there, for example around Bregenz.