Curious however about recommendations for VoIP providers in .ch there
aren't that many around unfortunately. would love to hear some suggestions (backed by experiece).
We have a redundant SIP uplink (2 different datacenters) to upc-cablecom. Pricing is OK, quality is OK, support is very professional (no 1st-level crap, you get directly to the engineers). They use a separate physical connection for the VoIP link and run a VPN on that link between your PBX and theirs, so you're not exposed to DDoS and other nasty stuff from the Internet. Of course it's still a good idea to protect your PBX with a session border controller and a firewall... ;-)
This setup exists for 3 years now and I don't see any reason to change providers.
Kind regards, Viktor