Rayioprien73 Within Switzerland, 0800 800800 is free of charge (from Swisscom side even from abroad), regardless of which provider you have, but you can also arrange a callback or use the chat function, via the contact page so that you will be called back at the agreed time.
Residential customers: contact us via call, chat, text | Swisscom

Btw. Please read, what the Swiss authorities (BAKOM) are saying about 0800 numbers
Other numbers: free of charge or not? (admin.ch)
